what is the limitation for number of roles and profile that can be assigned to a user in salesforce?
A user can only have a single Profile and Role assigned to them. The screenshot below shows the Edit User screen where you can set the Profile and Role
Another option to grant permissions to multiple users are Permission Sets. Multiple Permission Sets can be granted to each user
You can also use Public Groups rather than Roles if you want to group users together. A user could be in multiple Public Groups.