“Roll up a dollar bill”

LUKE: Fresh coffee will be ready in a minute, unless you wanna just roll up a dollar bill and go nuts.
LORELAI: No thanks, I can wait.

Luke is saying sarcastically that if Lorelai can’t wait for a cup of coffee, maybe she could just snort up coffee grounds with a dollar bill, as if she is doing a line of cocaine. It’s a comment on how much of a coffee addict he thinks she is.