being that generally the 'attachment' is not actually part of the forklift, they are usually made by a different company such as cascade or longreach, bolzoni etc.
it should have a dataplate on it somewhere
if we had this information it might be more helpful

what kind of clamp is this?
bale clamp?
roll clamp? (i assume this is it since you said 'mill roll')
rotating or stationary clamp?(i assume it does this being a roll clamp?)
going on what edwardt says, is this swivel block part of a hose reel? or in the center of the clamp? If it swivels where the hoses connect to the attachment at the carriage then what edwardt says is correct, there are other ways they use now to connect the hoses and allow for the hoses to traverse up and down without the swivel block.
But if this is a rotating clamp then i'm thinking the block in the center of the rotator.

need more info