You have to take action. But start with the roommate.
I would start with “I have been smelling something kinda bad in our room and I think it is coming from your top drawer. Do you think you could wash everything in that drawer? I think it is starting to spread.”
Give them a day or so and if that doesn’t work go to the RA. Say that you are worried about mold and it being a health issue. They will ask you if you have talked to the roommate and you can say yes that you did.