TL;DNR: As usual, the answer is, "it depends." In this case, it depends on whether you ever worked on this deal while you were in the state that requires a license. US courts have consistently held that a broker or agent who is not physically present in a state is not "doing business" in the state, and thus not subject to its licensing laws.
First, a point ...
do I have a case against them in small claims court?
Yes. Your description altogether indicates that there is --at least-- an implicit contract between you and the roommates. That implicit contract is palpable from the roommates' subsequent conduct, which includes --but is not necessarily limited to-- their excuses and promises.
Although there is no ...
It’s very generous of you to provide your roommates with free electricity and internet
Because, unfortunately, that’s what you’ve done.
The law doesn’t care about “expectation” it cares about agreements, specifically, agreements that meet the threshold to be a contract.
Make a written one with your future roommates.
You have two downvoted answers here. One of them is actually correct, one is nonsense. Question: Which one?
Answer: Doesn't matter. If you provide this service without getting advice from a competent lawyer first, your risk is much too high. Making the wrong decision (either giving up on a good business idea without reason, or providing a banking service ...