Put the roast in a slow cooker, cover with enchilada sauce (about 1 to 1½ cans depending on size of roast) and cook on high 6 - 8 hours, 2 hours before it is done shred the meat.
Shred the Cheeses into separate bowls.
Make and assembly line with tortillas, meat, & cheese
In 12" Non Stick Skillet heat 1 stick butter with 1 - 2 Tbsp oil over medium heat
Heat tortillas in butter & oil mixture, one at a time, on both sides until soft. Move to cutting board and fill with meat and Jack cheese. Roll and place in Baking pan. Repeat until pan is full. Enchiladas should be packed tight.
Cover enchiladas with enchilada sauce (1½- 2 cans) be generous or the enchaladas will be dry.
Top with optional ingredients & cheddar cheese
Bake at 425º until cheese melts and sauce is bubbling, about 30 - 40 minutes.