PaperUI is not intended to be a User’s Interface. It is an Administration Interface. Therefore your “want to turn all three lamps over one switch” is not something PaperUI will support. The “room” concept only applies to Things and only within PaperUI.
You will need to:
Create Items that link to your Hue Things
Create a Group and add your Items to the Group
Create a sitemap or HABPanel UI.
a. Create a section named "kitchen"
b. Put the Group on the sitemap or HABPanel using a Color element.
1 and 2 can be done within PaperUI. For 3 you need to follow the docs for sitemaps or habpanel.