To capturing object properties per pass you use the 'Properties' tab. You can create sets and then add objects, or select objects and use the create sets button and RPM will offer to add the objects to the newly created set.

Object properties are automatically captured and restored as you change passes, so you can simply set up each pass as you need to. Turning off the yellow 'Auto capture props on pass change…' buton disables the capturing and restoring, and for a temporary disable you can turn off the 'Restore Render Params (always on for render)' checkbox tht is the in 'Global Viewport Params' below the pass list.

Pressing the 'Create Set' button brings up the Capture Set Parameters, dialog, where you assign which properties will be captured on the objects that are assigned to the set. Items highlighted in a list will be captured, non-highlighted ignored: you can un-highlight a previously captured property and RPM will ignore that property from then on. When you press the 'Ok' button, the properties are captured and the dialog closes. The Apply button allows you to set and capture the properties but leave the dialog open.

Note that while you can assign any object types - meshes, lights, cameras - to a set an capture properties relating to each (RPM won't try to set a light parameter on a camera for example), organisationally it can make more sense to break up your sets into different object types.