Bought alcohol for my college roommates

So when I smoke weed I get more weak willed and I agreed to buy alcohol for my college roommates. Both being 19, I’m 23.

I’ll likely keep an eye on them when they do drink at the house. I told them I’d get it for them but they have to be responsible with it and I asked them where they plan on drinking it and they said at our apartment.

I feel guilty for not saying No, straight out. I most likely won’t do this again. Anything you can say to ease my guilt?