*Spoiler Warning for whomever considers this to be Spoilers*
I would say the entire tennis team (you meet them all at the beginning) is all fairly versatile in terms of on screen content, with the exception of Coach Grifter who has a preference for bottoming overall, but still tops once.
I think it's safe to say Dwayne is a bottom considering his route's only half way done, and he has already matched the number of times the Coach has bottomed.
And as for Richard, his route is also not finished, but honestly, I could see it going any way for him in the future, as of right now, though, he is only shown topping.
This recollection does not account for the number of non-dick-in-butt sex scenes. There are too many for me to recall all of them, but there's at least like 4 (probably more) in each route, with some of them being mildly kinky and roles may vary depending on whose route you're on. I guess it just depends on what actions you would identify as "Top/Bottom Behaviour".