I'm not going to give my roommate his share of the profit from our business
What will happen if you do not give him his share?
I'll be able to use the money to buy luxuries that I want.
I think it is very wrong to hold on to money that belongs to somebody else, so you should give it to your roommate. Such behavior is simply stealing and it can land you in jail, if you do it. Despite your greed, I think you should give your friend his money, and just start saving more yourself.
I will beat him up and teach him a lesson.
If you beat your roommate up, you'll only end up in even more trouble. You'll already be in trouble for not giving him his share of the money, but he could also have you arrested for attacking him. Just give him what he's owed and move on with your life.