Legal Issues with Turning in Drug Dealer Roomate

I am currently about 8 months into a joint 12-month lease. My mother is also legally associated with the lease as my co-signer.

I allowed my roommate to have and use marijuana in the apartment. I partook in it as well during the second and third months.

About two months into the lease, I then allowed my roommate to start dealing. All the drug deals went down inside the apartment. All of the drugs and paraphernalia was confined to his room and a semi-common area. There may also still be LSD, which I also partook in a couple months back.

I had started to become uncomfortable with the use of marijuana in the apartment, but didn't say anything. Around that time, which was early December, I found a bent spoon. I thought it was strange how my roommate managed to bend the spoon at almost right angles, but didn't think much of it and just bent it back.

I went home for the holidays for about a month, and only just returned. This time, my mother found two bent spoons and informed me that they very much looked like they could be used for heroin or cocaine. There however were no scorch marks on the bottom.

I, of course, will be talking to my roommate to try and sort things out. But if I'm not successful, I would like to know what my next step should be.

What, if any, legal sentences could I receive if I turn him in?
What about if the landlord or police discover him? Would I be prosecuted too for not alerting the authorities?
What steps should I take to ensure my own legal safety in these situations?
How would my mother be affected by any of these situations?