PC12 Captain reported a critical ground conflict during landing rollout with a departing helicopter on intersecting runway. Both aircraft had received appropriate ATC clearances. Captain suggested a LAHSO clearance would have prevented loss of aircraft separation.

Narrative

After being cleared to land on Runway XX at ZZZ; we were advised of a Helicopter to our south. We notified Tower that we had the Helicopter in sight; and they advised us that they would be landing on runway YY (an intersecting runway). Tower instructed the Helicopter to 'remain south of runway XX at all times'; to which the Helicopter crew responded that they would comply. We were assigned number 1 to the field; and subsequently landed ahead of the Helicopter. As we were rolling down runway XX; headed for taxiway Foxtrot (our ATC assigned clearing taxiway); the Helicopter landed on runway YY. Shortly before they had touched down; tower had cleared them 'for the option'; and once they had landed; I noticed that they were rolling; but not slowing down.It became clear that they were accelerating for takeoff; and we were approaching the intersection of XX and YY. I told my FO to slow down; so that we would not cross their runway. The Helicopter lifted off of runway YY only a couple hundred feet from the intersection of runway XX; and nearly immediately began a left turn and told tower that they would 'join left traffic'. At the point at which they lifted off; we were only maybe 100 feet from the intersection of the runways. This was very nearly a runway incursion.Tower and the Helicopter crew both seemed unfazed; which could be due to the National Guard being based there; so operations like this are common place for them. However; for a third party that is unfamiliar with this; it was rather disconcerting. We continued to the FBO ramp without further incident; and I did not make a big deal of the issue by getting the tower phone number; but in hindsight; it may have been a good idea to have done so; so that I could get a grasp on the situation from tower's perspective and ask some questions to better my own understanding.My suggestion to help avoid issues such as this in the future is to possibly create a presentation for crews to have a better understanding of the intermingling of rotorcraft and fixed wing aircraft. We have numerous presentations stashed throughout our various training locations on far less important topics; so I think a presentation on phraseology and operations associated with rotorcraft; versus what we are used to with fixed wing; would be a phenomenal addition to our training platform.I have no idea if 'remain south of XX runway at all times'; prior to a 'cleared for the option' clearance; essentially holds the same weight as a Land and Hold Short (LAHSO) clearance; when it comes to rotorcraft. I assume it does not; but I could be wrong. I also don't know who should have been issued a LAHSO clearance in this case; if it was necessary; I assume the Helicopter since they were number 2 to the field; but once again; I have no idea. Personally; I think a lot of the fault falls on tower for not clearly providing instruction to both us and the Helicopter crew. And in the interest of transparency; I genuinely don't know if anything that took place was actually improper or a violation of any regulations. If we were to create a presentation; perhaps a dive into the FARs associated with rotorcraft; as well as information provided by helicopter pilot(s) and air traffic controllers; specifically those from a tower environment; would be immensely valuable to our operations. I know this situation is fairly rare; and was comprised of numerous layers leading to this outcome; but to simply improve the understanding and expectations of our crews when intermingling with rotorcraft; in and around the traffic pattern; could be priceless.