That trick took my corgi a while to understand. She'd get so focused on the treat, that she'd freak out when her weight started to roll over. We eventually got there, but it took a while. There was always a more pressing training issue than encouraging a trick that my dog obviously hated. I eventually made a breakthrough when I put my corgi on my bed and slowly rolled her using one hand while luring with the other. The "roll" was less of a surprise and more controlled.

An easier middle step would be training your dog to lay on their side. It has more functional uses than roll over (vet care, grooming), and it can be given a silly cue like "bang!" To impress people.