Premis metadata

Supports Omeka the PREMIS Data Dictionary?

There is not a specific element set for PREMIS but you can edit the item type fields for each item type to make the Omeka fields work with that metadata:
http://omeka.org/codex/Managing_Item_Types.

Or, you might try creating an element set through a plugin for PREMIS. See here for more information on creating element sets: http://omeka.org/codex/Creating_an_Element_Set