CRJ 200 pilot reported a fuel truck crossed their landing runway with less than 1500 feet of separation as they were decelerating after touchdown.

Narrative

As we were approaching ZZZ at night; we were aware that Tower was going to close soon as we were slightly late. We were switched to Tower from Approach on the downwind and was told to report base. After reporting a 5-mile base for runway XX; Tower clears us to land on XX and approximately two minutes later; Tower announced that it is now closed. Fast-forward to short final the runway intensity lights were changed from medium to high. As we were decelerating; we decided to vacate the runway at the end and we both shockingly see a fuel truck crossing the runway without any form communication. They simply crossed the runway with less than 1500ft of separation as we were still on the runway. We even tried to reach them on frequency but there was no response. We taxied safely to the gate without any further occurrences.Cause: Failure of ground personnel in fuel truck to recognize aircraft on the runway and failing to announce movement on an active runway. Suggestions: Highlighting importance of active runways and runway incursion avoidance training for ground personnel. Using handheld radio to announce intentions and movement on the movement areas of an airport.