Dryer drum very noisy with a lot of vibration when operating

Removed lint filter and 2 screws on either side of lint filter housing. Pried front part of top panel up on both sides and flipped backwards out of the way. Disconnected wire to door-open switch. Supported top panel with a standup dolly/handtruck so that it didn't put stress on the back mounting clips at the back of the top panel. Removed 2 screws securing the top of the front panel to the two side panels. Lifted the front panel up to release it from the clips at the bottom of the two side panels. Set front panel aside. Laid (layed?) dryer on it's back. Lifted out drum, removed old belt. Removed screw holding base of strut to bottom of dryer frame (left support roller when facing front of dryer). Pried off push-on washer/clip securing strut to roller shaft. Pried off triangle washers holding rollers on shafts. Vacuumed loads of lint out of the inside of the dryer. Reassembled in reverse order. A little tricky getting the belt back on the drum, through the pulley/tension wheel and around the motor spindle/spool thingey. With the machine still laying on it's back I wound up using masking tape to hold the belt onto the middle of the drum while threaded the rest of it into place to the motor.
Problem was due one of the support rollers having a flat side instead of being round.