Guillaume Rostand — Co-Founder, Fractional CFO

Founding Partner & CMO

Guillaume co-founded Iter Advisors and runs its growth function. A former SaaS-startup founder, he spent a decade on the operator side before switching to advisory. He leads the firm's marketing, partnerships and business development efforts.

At Iter Advisors, Guillaume leads the firm's growth and marketing strategy, with responsibility for positioning Iter Advisors as the reference fractional CFO resource for European tech founders. He works closely with the CFO team to translate deep financial expertise into practical guidance — publishing in-depth guides on outsourced CFO models, financial tool stacks, due diligence processes, and startup finance strategy read by thousands of founders and finance professionals each month. As a former SaaS founder, Guillaume brings first-hand experience of the financial challenges that growth-stage companies face: managing investor relationships across multiple geographies, choosing between outsourcing and in-house hiring, and building financial systems that can absorb rapid growth without losing control. He has been directly involved in more than 40 founder relationships at Iter Advisors, contributing to commercial strategy, market positioning, and team formation across France, Spain, and Belgium. Guillaume is based between Toulouse and Barcelona, holds a degree in Engineering, and speaks French, Spanish, and English. He contributes regularly to European startup conferences and mentorship programmes on sustainable growth and financial operations, and is committed to making expert CFO knowledge accessible to every founder regardless of company stage or sector.