Roulette for pros is far beyond the bets and the numbers showing up. It is in most cases related to the number of bets and the stakes they play for the day along with money management plans.
Pros in roulette essentially play one full session. When they are coming for the day, they have a bankroll, they have a decided risk threshold beyond which they will not play, they have a plan for loss for the day, and they have a plan on when they will stop playing.
They are going to have their betting system focused on a profit/loss for the session they are going to play. They do not play in a way to re-cap the losses/profits of yester-plays.
Every session is new and every session they play in roulette is marked with a bankroll. Regardless of the kind of betting system they follow, be it the Martingale, Anti-Martingale, Parley progression or Fibonacci they apply it for one session, which will consist of a pre-decided number of spins.
Pros normally are aware of the risks in the game and they throw in their money being aware of the shark loss they might suffer. They do not sit to gamble without a piled up bankroll with a structured betting system that they are going to use. This does not mean that pros are going to play just millions or thousands. Just to say that they are aware of how to split even a $10 bankroll between 100 spins or 75 spins making one session (a number of spins) of play.