Is he though? His ceiling might be, but I think his floor is pretty high. I feel like Byfield is a 'riskier' pick (in the sense of what will he end up being) and yet you seem to be under the assumption that hes Ottawas guy.
There are a number of factors that make me think Rossi will be perceived as high risk:
1. Size. He's small. There just aren't a ton of guys his size that are top end players in the league. Sure there are some - Marchand, Gaudreau, Marchessault - but they're still rare. Also note that very few of these players are checkers. At this size you have to produce or you don't play.
2. Perception among some scouts that he's physically mature. If this is the case it caps his upside. Simply less growth potential.
3. Scoring splits against good and bad teams. He beat up on bad teams at a disproportionately high clip. Inflated stats?
4. Age. One of the oldest players in the 2020 draft. I don't put much stock into this personally, but I know some do.
5. Skating. Lacks elite speed.
I'm not saying that Rossi will bust. I don't know that. I'm saying that if he's one of your preferred options at 5 I think you're likely to be disappointed.
Regarding Byfield - I don't think teams regard 6'4, athletic, skilled centers as risky. Certainly not to the extent of Rossi.