What a bad luck, I thought that after payment system tests, and when I jump to Junior Member rank I will be able to join.. and now this informations.. 
Even if you already become Jr. Member, you still cant join this sig campaign, because coinroll just accept from rank Sr. Member or above in their sig campaignAre you sure?
As i wrote i have been waiting when payment system test will finish. As wrote Namworld after this time they should open this campaign for all users:
we're running a test campaign. For now, only Sr. Member and up can register as links require [size] to work. Links may change later as all members become allowed to advertise for us.
All" - I understand that Jr. Members and maybe even Newbies.