I would tie it into the RV electrical panel. I would just use the circuit breaker that formally went to your roof AC unit.
If this unit is 120v that makes it easy. Most of the mini-split's I'm familiar with in residential construction are 240v AC. I would make certain this one is 120v. However, a 240v unit will work just fine if you have or can install a 50 amp service in your RV. The 50 amp service will provide 240v.
If this unit made for office trailers specifically? If it's intended for stationary use I would wonder if the manufacturer will warranty it when used in a mobile environment.