ROM first started out as a toy action figure developed by Parker Bros in the States. Similar to what Hasbro did with the 3 3/4 inch GI Joe line, Parker Bros approached Marvel asking them to do a comic on the character. The ROM Spaceknight comic actually outsold the toy by several years.
Palitoy acquired the license from Parker Bros (Palitoy also had licenses for many Parker Bros board games) to release ROM into the british toy market and when they did so, they decided he would be a natural addition to the Action Man range. So its safe to say that Palitoy never intentionally developed the ROM Spaceknight idea for Action Man they just saw it as a good opportunity from a marketing perspective.