I certainly wouldn't say that alcohol would weaken your roll. At the beginning of this year I rolled on molly crystal REALLY hard, taking on avg 300 mg, about once a week for 4 months, and I chose to get drunk pretty much every time because I was in my last semester of university and that's all people do at parties and whatnot, and if I wasn't drinking but having the time of my life like that others would wonder what's up with that extremely happy dude haha. Plus I enjoyed drinking all night as it was a normal vice at that time in my life, and drinking with your rolling buds is a hell of a time, great to connect through it, you will have the best predrink of your life haha. I would have upwards of 10 drinks and it really didn't affect my rolls, maybe made the nights harder to remember, but rolling memories always seem like wonderful dreams that go by so fast and fade away rather quickly anyway

I have no noticeable long term problems from this usage, was taking a pile of 5-htp as well. I actually found that molly would significantly reduce hangover symptoms, which I almost always would normally have from alcohol, and which were god-awful. I don't know, maybe it makes my body process it differently, or maybe it's because I hadn't abused it long enough to start getting downs, and was basking in incredible afterglows afterwards for days. But I wasn't drinking anything but booze when I was on it, and so long as you know it's mdma and nothing else, I would say this is a relatively safe thing to do if you can handle your booze, but definately unnecessary and I will never repeat this again because nowadays I worry about long term effects from mdma since I am more informed thanks to this website.
Oh, and I would never have anxiety on the come up if I drank a little beforehand. If it is worth mentioning I railed my molly as well, which I LOVE to do, made me fly for hours each time, and I would rather damage my rather unharmed nostrils than mixing that shit in with booze in my stomach and further hurting my probably ravaged internal organs. So if you're taking your stuff orally this might be an even worse idea.