Food Allergy?

I'm new to this forum and initially posted this in another area. I hope it's okay to repost it here. I picked up my 12 week old Shih-tzu puppy, Brody, from the breeder on April 9th. The breeder had been feeding the pups TLC, a top Canadian brand. I purchased the same and shortly after getting him home I noticed he was scratching his ears and licking his paws. I gradually switched him to 4StrongPaws, a grain free Canadian brand and I've noticed the paw licking is starting to ease up but not totally;however, in the morning he'll be laying on his back in his crate rolling back and forth and moaning, at least I think he's moaning, like he's trying to scratch his whole body. His ears are pink and look great. There's no lesions or hot spots and his paws look perfectly normal, but he'll lie on his back rolling back and forth in the morning and sometimes once at night, like it's his job. I've heard that if you change a dog's diet, in the hopes of improving a situation, that it can take up to three weeks before you see a change. I think I'm dealing with a food allergy here but I'd appreciate I an opinion.

Hi

I think the worst indication of food allergy would be like diarrhea and vomiting. Just to make sure, take Brody to the vet

My male Beagle does this rolling around just for pleasure, but if you think it is more than that, have you checked your puppy for flea dirt and cheyletiella, (a rabbit mite)? If there are any signs of dandruff, I would try an anti mite shampoo.

My staffie loves rolling around on his back, legs in the air and kind of moaning, I think he just likes it, his skin is a clear as can be. He often sleeps like it too. I understand the ear scratching and paw licking could be an allergy but if his ears look pale pink and healthy then even that is questionable. The only way to know is an exclusion diet tbh. If you change food again go for a grain free with a completely different protein source.