I am not saying that roster rules should revolve around the odds markets BUT there are certain safeguards that are in place for certain sports.
In soccer, a player can have odds listed in various stats markets, HOWEVER if he is on the subs bench and never gets in the game, the bet isn't lost, instead it gets voided.
In baseball, the games will have projected starting pitchers listed beforehand. Again, if that specific pitcher doesn't actually appear then bets become void, they don't lose.
Of course, swinging the other way I can give you basketball examples.
A star player has odds to score x number of points or gain x number of rebounds and things are going great for three quarters. However, his team are beating the crap out of their opponents so the coach decides to pull him out and rest him the entire fourth quarter, so he misses the "over". That's just tough luck for the gambler who simply needs to accept the loss.
In the same way, a lowly bench player has the same odds, with the bettor surmising one of two things will happen. Either, the team plays great and this player never sees the court (hence void) or the stars get in injury/foul trouble so this player sees a lot more action than he otherwise usually would (better chance of win.
What happens instead? The stars stay in for a massive chunk of the game, and our bench warmer only comes in during 4th quarter "garbage time" so he gets 3 minutes of doing nothing - but because he's been on the court for 3 minutes, all bets on him stand. Again, anyone taking "overs" just has to suck it up.
(In case anyone is thinking "I strongly suspect personal experience in this post" yes you'd be right).
But like it or not, CFL betting is guaranteed to be offered by someone, somewhere and things like injury reports and roster composition WILL have an effect. Why do you think NFL pre-season point lines are always lower than the regular season? Because the odds compilers know by the second half you'll be seeing the 4th string QBs playing each other.