I'd always recommend a typedef with function pointers. Then, you would write:
// Make sure to get the function's signature right here
typedef uint8_t (*GetRole_Ptr_T)(char const*, UsertoRole_T const*);
// Now initialize your pointer:
GetRole_Ptr_T getRole_ptr = Authorization_getRole;
// To invoke the function pointed to:
given_Role = getRole_ptr(userId, roleTable);
Regarding "Where do I initalize the function pointer getRole_ptr?": Depends on your requirements. You can do it when declaring the pointer, as I did in my example, or you can change the pointer later on by assigning to it:
getRole_ptr = Some_function_with_correct_signature;