We don't know too much about Patrick's pot-dealing friend, except that he throws a lot of parties and smokes a lot of marijuana—probably in his parents' basement.
Everything we learn about Bob comes in Charlie's letter from May 2, 1992. Here, we find out that Bob is a whiz at Mary Tyler Moore trivia, he showers every other day, he wants to be a chef, and he goes to the local community college part-time. Not the most dynamic character, but at least he has a personality.
Were it not for the whole drug dealing thing and the fact that his brain is probably baked beyond repair ("After you've known him for a while, he starts to repeat these things. In the last few weeks, he hasn't said anything that I haven't heard from him before." [4.2.6]), he might be a successful guy.