The difference between Don Tortaco and Roberto's?
Virtually nothing at all. I wouldn't be surprised if I found out the owners of the two similar franchises were siblings just competing against each other.
They use practically the same ingredients and all the foods taste/look/seem the same, just claimed by a different franchise tag.
Blindfold me and bring carne asada fries from each place and I won't be able to tell you the difference. Just like Roberto's, Tortaco's meats are mediocre. Way too grilled and doesn't even take like authentic carne asada. I'm not Mexican but I lived on Mexican food so I know what my asada and pastor tastes like~
Despite its annoying similarities, it's not bad. It's worth going to here and then but nothing special. I would go maybe if I was intoxicated enough and since it's close to me.