You can submit your application first without the GMAT. RSM ensures that if a programme closes earlier than January 31, you have until at least 31 January to provide your GMAT results. After 31 January, if your GMAT results are still missing when the deadline has passed or the programme has filled up, the application will be rejected.
If you submit your application early (between October and December), the RSM Admissions Office can already evaluate your academic background and give you an indication regarding your eligibility, even when your GMAT scores are missing.