At leasat on Royal Caribbean the tender boat used is somewhat tour dependent. I'm not sure any of them were roll on tenders but I wasn't watching specifically for that type of tenders. The tenders direct to Samana was the ship's lifeboat. There were other tenders in use that took you to specific locations like direct to Cova Layo (I think that's the name of the beach used as a beach day). Depending on the tides don't remember being able to go straight out from deck 1 to the tender. Sometimes it required one step and sometitmes several steps to get to the proper level of the ship.