<human>: First self-post so go easy on me please.

I just graduated college and I'm back in my hometown, and have been seeing a lot of old friends, hanging out, drinking, etc. There's one boy in particular that I've known for a while but never had the chance to really hang out with and get to know, but I had a little thing for him in high school. We can call him Tom. 

Recently he's been calling me to hang out with him and his friends (and some mutual friends) and we've been alone a couple times riding bikes around and driving places and get along really well and it hasn't been awkward at all. It's actually been pretty nice. I'm really interested in a relationship with him and even got the blessing from a few mutual friends. 

The complication is Tom's roommate. I just met him this summer and he's a cool guy. He and Tom are friends and went to school together( but I don't know how close they are.) The thing is I'm starting to get worried he may like me. He's sent me some texts that I consider flirty but also could just be friendly (asking if I got home ok, complaining about a hangover the next morning). He has also written on my facebook a couple times.

So. I may be over-thinking things but I'd like to get some advice in case he is interested in me. I have no real problems with him (like I said he's a fine guy), I'm just not really interested in him.  What do I do if he makes it obvious he likes me? Do I say "no" and tell him that I prefer Tom (and make a relationship with Tom potentially awkward for him and his roommate)? Do I say "no" and provide no reason (I just don't want to lie) and see if things work out with Tom on their own? Do I say "yes" and give him a chance anyways, and possibly make things awkward and discourage Tom? 

Am I over-thinking this whole situation?

Can you succinctly summarize the text in 1-3 sentences?
<bot>: I like a boy but worry his roommate may like me. What do I do if his roommate asks me out and I'm not interested?