IIRC The Gen 1 was available as a .357. The Bloomfield Crosman factory is about 30 miles from my home and I heard of them from an employee in the early days of Gen 1.
Like stated above, not aware of any production 357 marauder. The platform is a bit of a stretch to do that cal. Crosman does build prototypes and has many on display at Bloomfield. Maybe early on the Rouge was considered to go under the Mrod name?
Please post a picture. Inquiring minds like to know.