Should I tell my roommate to drink less tea
Are you thinking that your roommate has a tea drinking problem?
No, I just want all the tea to myself.
It's nice that you like tea but being selfish with it isn't the answer. If your roommate also likes tea a lot, then maybe you two should buy separate supplies.
I'm just going to tell them to stop drinking the tea.
In a roommate situation you really have no right to control what they eat or drink. A solution to these types of issues with roommates is for both of you to purchase your own groceries. Then you can both happily consume the amount of tea you want.