In this case the designers tried to come up with a ship that could carry roll-on-roll-off cargo, containers, break-bulk and refrigerated cargo. The result was a ship that could do all of those things, but could do none of them very satisfactorily. Although fairly large ships, they could not accommodate enough containers to compete against the specialized container ships that began to appear at that time. There were no internal ramps, so roll-of-roll-off cargo could only be accommodated on a single deck and, in addition to that, the fact that they were steam turbine-powered meant that access to the forward end of the roll-on-roll-off deck was obstructed by the engine uptakes. For those reasons, they could not compete against the specialized roll-on-roll-off cargo ships that also began to appear at that time either. These ships were all right as break-bulk ships, but the container cells below decks got in the way, and the large, open roll-on-roll-off upper deck made it equally difficult to secure break-bulk cargo properly. In addition, the refrigeration system in the lower cargo holds proved to be a maintenance nightmare, and wasn't even functioning any more when I was on board. The end result was a sort of seagoing "Jack-of-all-trades-and-master-of-none".

Thanks REG for your very informative comment and I will delete the USNS subtitle.
I like your comment about ships that can do "everything" - ok on the drawing board perhaps but arranging different cargos could be a logistical nightmare for the owner!

Incidentally, these ships were originally intended for Moore-McCormack's Baltic trade route, where it gets very cold. For that reason an unusual feature of these ships was a tiny enclosed and heated cabin on the bow for the lookout, which can be clearly seen in this photo. These were the only ships that I ever saw that had any such thing.

I spent six months on this ship during 1990-91, transporting ammunition to the Persian Gulf during the Gulf War. Actually, despite the battleship-gray hull, she was never called "USNS Rover" because she never belonged to the Navy. Technically she was a merchant vessel, and was therefore referred to simply as "SS Rover", because she was owned and operated by Central Gulf Lines (note Central Gulf Lines' colors painted on the funnel), and only operated for the Military Sealift Command on charter.

The Rover was overdue for an overhaul in the shipyard, but that had to be postponed when Iraq invaded Kuwait. Consequently, the ship was in pretty bad shape, as is evident here. Nevertheless, we managed to keep her going for the six months I was on her.

She was originally built for Moore-McCormack in 1969 as the Mormacsea, one of their so-called "Sea-Bridge" class of cargo liners. They were a very unusual and ambitious design, combining roll-on-roll-off ramps with container cells and refrigerated cargo holds. I always had the impression that the designers had attempted to produce a ship that could do everything, but that they ended up with a ship that could do none of those things well enough. In any case, she was soon sold to American export Lines and renamed Defiance. Over the next couple of decades she changed hands several more times, being owned by Farrell Lines (as Defiance), U.S. Lines (as American Rover) and finally Central Gulf Lines (simply as Rover). I believe she was finally scrapped in 1993.