Blacks were used to move equipment. The last bill passed in March, 1865 made law that Negros could be under martial arms, that women under forty years of age could be subject to the draft and that the Third National be the flag of the Confederate States of America.
Free Blacks were used on vessels of the south as seamen, many of the cooks were plantation slaves. I doubt any Afro-Americans were on the rolls of the CSMC, unless it was a headcount of available manpower.