Add the potatoes to a slow cooker with the olive oil, onion powder, garlic powder, dried thyme, and dried rosemary. Mix to combine everything and put the lid on. Cook for 3 hours on high. The potatoes are done when they're fork tender.
Add the butter and stir. I also like to add a little salt & pepper here, but season to your own tastes. They're ready when the butter is melted.
To serve, I like to spoon a little of the butter from the slow cooker over the plated potatoes and sprinkle some parmesan cheese on top. Enjoy!
Notes
If you want to double this recipe, I recommend giving them a stir at the half-way point.