Actually, it would affect the reputation of the site overall based on how the sportsbook performs. For example, look at Stake. Their sportsbook section is plagued with issues due to which many gamblers primarily visit their site only for their casino games.
That is very true because they have so many problems that a few friends on my telegram said that they are not going to make sports bet anymore on stake and rather chose a better platform because they deposit and get ready to bet on big events and then the site goes down which is really frustrating.
Adding a sportsbook section is probably not that difficult for a heavyweight like Roobet, but building it in such a way that it can directly compete with popular crypto sportsbooks like Cloudbet, Sportsbet is the difficult part.
They just need to combine with odds provider and add it which is not a big issue and talking about being competitive they can always lower the house edge and offer the best odds if they want, I actually think if Roobet launches their sportsbook it would be best by a big margin.
Why would anyone bother with a subpar sportsbook when they could wager in an above average dedicated crypto sportsbook?
Well, because people do not visit different sites for different needs like if I am rolling dice on stake I would usually gamble there for sports too barring downtime.