I'm going to snitch on my roommate for smoking in our apartment
Why do you want to snitch on him?
I hate the smell, and I can't take this anymore.
Your annoyance is totally understandable but you should talk to him about it, because snitching sends the wrong message. I hope he'll understand that how much you hate the smell of his smoking.
I would snitch if I wasn't afraid of becoming a coward. I'm afraid he'll feed me to the bears.
Telling on people does put across the idea that you are cowardly, and it shows weakness. Be strong and confident in speaking with your roommate about your issues so that you can work things out.