It was common for warriors with German names to change them, partly as a statement of patriotism but also for fear that if captured they would be taken for traitors and shot.
Roslieb's figures seem to represent Ferdinand and Isabella considering the conquest of the world, though I could well be wrong, especially as Ferdinand is usually portrayed clean-shaven.
Isabella examines what looks like an atlas while Ferdinand stares moodily at a globe, one foot resting on a couple of books.
Why Ferdinand and Isabella? Does anyone know the original purpose or owner of the building?