I was tearing down a 5.3 I purchased and noticed all the rollers in the lifters are not round and have flat spots, one lifter was seized and looked like it was ground flat. What would cause that? Lifter were slightly different than what was in my 5.3, the rollers in mine were exposed on the sides and end, these lifters rollers were surrounded except for the end. Motor was running when pulled

 

Got pix...………………..

 

The full encapsulated lifters are the newer design known as the LS7 lifter. The ones with the exposed wheel are the early design.

Likely a lack of lubrication caused the damage. It's not uncommon for people to run these engines low on oil and go way past the recomended service intervals based on the Idiot Maintenance light.

 

I change my oil based on the idiot light

At 188k, no idea what she looks like in there, but no ticks! Yet. Mobil 1, every 5-7500mi depending on the idiot light.