From Engineering to the CFO Seat: Johnnie Walker on Building Rooled

The trap that catches solo fractional CFOs

When Johnnie first worked as a fractional CFO, he ran into the same problem most solo operators face: you end up doing everything.

"You often end up doing the entire stack of work that a client requires," he explains. "Everything from what you really want to do, like board interaction, strategy, and financial modeling, all the way down to the fundamental accounting processes."

The issue isn't just that strategic work is more interesting. It's that the basic accounting work requires a different skillset entirely. You want to focus on the strategy side, but you're probably not the right person to be doing detailed bookkeeping and reconciliations. That work needs skilled hands with deep expertise in the fundamentals.

Until you grow your practice large enough to employ someone, you're stuck. You can try leveraging outside resources, but quality is variable. This is why Johnnie sees building a reliable accounting function as essential infrastructure for any fractional CFO who wants to scale, and why he and his partners built Rooled to provide that full stack.

The skill that actually separates successful fractional CFOs

Ask Johnnie what makes a fractional CFO successful and he doesn't start with technical expertise. He starts with relationship management.

"So much of this work is multi-relationship management," he says. "You're not under an employment agreement with clients. They can cancel your work at any step if they don't like what you're doing."

The fractional CFOs who build lasting practices are the ones who can anticipate problems before they become crises. They never let a client reach the point of frustration. It sounds basic, but that proactive client management is what separates operators who build sustainable businesses from those who burn through relationships.

Technical expertise matters too, but it's table stakes. Client management is the differentiator.

How to build credibility as a fractional CFO

For finance leaders entering the fractional market, your reputation is your pipeline. Johnnie's advice: focus on building provable experience and strong referrals.

"The first thing you need is a personal referral, someone who has actually worked with you and can vouch for what you know," he says. Beyond referrals, look to build factual evidence of your expertise. Have you worked with companies at specific stages? Can you point to clients who would speak to your work?

For founders evaluating fractional help, look for that same evidence. Does this person have a background in startups? Have they worked with companies at your stage and scale? Can they demonstrate relevant experience, not just adjacent finance credentials?

AI flux analysis is the real use case right now

Johnnie has completed AI courses and spends time understanding how LLMs actually work. That gives him a sharper filter for evaluating platforms making big AI claims.

The use case he sees consolidating across multiple platforms is flux analysis: comparing two periods in financials and understanding what changed.

AI streamlines this by putting words around the data and automatically surfacing the biggest movers. What used to require manually digging through general ledger details now happens with much more automation.

But the real power comes when you connect financial data to operational data. Payroll broken down by person and department. Sales pipeline trends. Operational metrics from across the business.

Why finance teams should be cautious building custom AI tools

Despite his engineering background, Johnnie is measured about finance teams building custom AI tooling.

AI makes software development easier, but the ongoing management, security, and maintenance still requires dedicated development resources. Building something is one thing. Keeping it reliable and secure over time is another challenge entirely.

He codes things himself, but with clear boundaries and an understanding of the risks involved. For most finance teams, the better path is mastering platforms purpose-built for finance workflows rather than trying to roll your own.

His advice when evaluating AI platforms: cut through the hype by asking what the AI is actually doing. Request a walkthrough of how the AI functions in practice. And ask about data handling. Where does the data go, and what contractual structures limit reuse? You have every right to understand what's happening with your financial data.

What founders constantly get wrong with investors

Two patterns show up repeatedly when Johnnie works with founders preparing for investor meetings.

First: not knowing the numbers behind the numbers. When you put financials in front of an investor or board, they're going to ask questions. The CEO needs to understand what's driving those figures. You can't defer every question to your CFO.

"The best CEOs I've worked with really spend time with their CFOs to make sure they're up to speed," Johnnie notes. That preparation separates founders who inspire confidence from those who create concern.

This echoes what Cassie Young shared on Johnnie's podcast, Speaking C-Suite: the best finance leaders can articulate the numbers and have a clear plan around their assumptions, including what adjustments they'll make if targets aren't hit. The best operating plans marry top-down ambition from founders with bottom-up planning from functional leaders. That alignment only happens when CEOs and CFOs build that partnership deliberately.

Second: misunderstanding what constitutes revenue. Early-stage SaaS founders often look at an invoice going out the door and think they've just booked that full amount as revenue. But under accrual accounting and GAAP, that revenue gets spread over the service period. Your ARR may have increased, but your recognized revenue is different.

This misunderstanding surfaces embarrassingly when investors look at financial statements and the numbers don't match what founders have been claiming. Basic P&L comprehension isn't optional for anyone on the exec team.

Advice for finance leaders going fractional

For anyone considering the jump to fractional work, Johnnie's advice starts with honest assessment of your network. When you step into fractional work, you're reaching out to your relationships to let them know you're available. You'll likely find some business quickly. The question is how you make it repeatable.

Expect slower progress than you anticipate. Many people's first fractional client is the company they just left, often at rates below what they'd ultimately charge. That's fine as a starting point, but plan for the ramp.

Find reliable accounting partners so you're not stuck doing work outside your zone of excellence.

And invest in learning the modern tech stack. There's real opportunity for fractional CFOs who understand the platforms that help startups scale.

"It's much easier now for an individual to get up the learning curve on platforms like Sequence," Johnnie says. "Then you can go to market and say, 'Here I am, I'm a CFO, and I really know how to get your billing done right.' If you're selling to the venture marketplace, people expect you to know the modern tools."

The takeaway

The fractional CFO market is growing, and there's real opportunity for finance leaders who build it right. The operators who create sustainable practices are the ones who manage relationships proactively, know when to bring in specialized help rather than doing everything themselves, and stay current on the tools that actually move the needle.

The technical bar keeps rising. But at its core, this is still a relationship business built on referrals and reputation. Both take time to build, and they compound over time for those who invest in them deliberately.