The Rock may be cooking in the WWE once again ... but some fans aren't super happy about it -- 'cause it seems his return has knocked a major storyline off track.
Here's the deal ... last night, Dwayne "The Rock" Johnson got into an intense staredown with current Undisputed WWE Universal champ Roman Reigns at the end of ESPN's WWE SmackDown -- an insane moment seemingly setting up a match between the two wrestlers.