I know its not recommended, but how bad is it to drink alcohol on roaccutane?

Roaccutane has a known side effect of causing liver damage in a subset of people who use it. The standard of practice is to monitor the liver function tests during use to stop it when signs of damage appear. Ethyl alcohol is broken down/detoxified by the liver cells and can cause liver damage when it must compete with other drugs for that process. Use at your own risk.

Alcohol is a poison that never did anybody any good, ever, so stay away from it. It is bad enough for a healthy person to drink, it is much worse for some who is taking medication. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV and Covid vaccines.