This is an interesting story, however, it would appear he did not volunteer, but was offered up by his Master for service while still a Slave. Slaves were quite frequently hired out for work by others, this is the first one I've seen hired out to the Confederate army. Would assume his Master collected his pay, allowances, etc.

Robin, Negro/Colored Cook, Co. D, 1st Battalion Georgia Sharp Shooters,* enlisted August 23, 1862 at Camp Anderson/Savannah by Capt. Dent, for the duration of the war, "Enlisted by Master as Company Cook," recorded present on the Sep & Oct, 1862 muster, pay due from enlistment, bounty due $50, paid on October 31,1862 including $50 bounty, recorded on the May & June, 1863 muster roll under remarks, "Company Cook (Colored)," last paid April 30, 1863, end of the year 1863, recorded as "Detailed as Cook," next muster as "{Colored) Company Cook," last recorded present September 16,1864, last paid on December 31, 1863, no further records

* This company was formed of details from the 29th and 30th Regiments Georgia Infantry and 8th Georgia Battalion and transfers from Savannah Volunteer Guards and 13th Battalion Georgia Volunteers, by S. O. No. 259, Hdqrs. District of Georgia

M266: Compiled Service Records of Confederate Soldiers Who Served in Organizations from the State of Georgia

By contrast, James Cansler, a Freedman of color, served as Cook, Company B, 59th Tennessee Infantry, served and was paid through June 30, 1863, however, he was detained by the Federal Army who assumed him to be a slave servant. He was not paroled with his regiment. His nativity was not recorded on his companies muster rolls. His Colonel commented:

". . . I had a freedman who did the cooking for my mess. A sharp shooter, who we supposed was in a tree, succeeded in striking one of the vessels he was using on the fire. He did not stop--only cursed the “Yankees” went on preparing such meal as we were able to indulge our appetites. He was a brave fellow. I was unable to get permission to bring him away after the surrender. (Col. W. L. Eakin)

Of interest, he was the son of a Slave who co-habitated with a German Farmer's daughter who bore him over three sons. One brother, Henry, crossed over the line and served as a white man in the 59th Tenn. Another brother, served briefly as a [Freedman] servant to the Col. & Lt. Col. of the 43rd Tenn., he was neither enlisted or paid.