Hmm looks like we would need to add to the devise configuration the spree mount point:

https://github.com/plataformatec/devise/blob/master/lib/devise/rails/routes.rb#L388

If you could just update this to still use spree.* I'll get it merged in.  Then either SpreeAuthDevise will need to be updated to set that Devise.omniauth_path_prefix setting or we'll need some sort of initializer for this repo to do it.