Hey, buddy. It's probably, because you actually are getting sized up. What you don't understand is that your mentality plays 100% into the d*ck-measuring contest that dominates their lives. For example, your roommate needs to feel like he's better than you at something. It's called being insecure.
I'm 31 now, and I spent the better part of my youth trying to prove myself. I never got in more trouble than when I went out of my way to show people up, make myself look good, and gain respect. Build up the guys around you, and you'll be way better off. Tell your roommate that's he probably right about the sprint. Compliment him on the gains he has had focusing on his upper body in the gym and rib him a little bit about "never forget leg day" or something along those lines. It shouldn't be an adversarial relationship, because at the end of the day, who the heck cares how much you bench? Does it really matter who wins a 100m dash between you and your roommate or that he thinks he can beat you?
If all you're after is respect and praise from the general public, then running middle distance is probably not the easiest route to achieve this.