Have created an Folder "Test" and a freestyle job dummy in it.
Have created an Item Role with regex "(Test/.*)" and all possible rights for Item Roles.
Have tested the link of the regex, Maching Project "Test/dummy" is shown.
Have assigned the role to a user and have restarted jenkins.
After login with the user, where the role is assigned, the folder is not shown and the user cannot create jobs.