Yes and no. from https://www.encyclopediavirginia.org/Lee_Robert_E_and_Slavery:
Yes, early in the war: “in a letter to his brother Charles Carter Lee, dated March 14, 1862, he praised the Confederacy as ‘the noble cause we are engaged in,’ and kept two of the Arlington slaves, whose manumission he was otherwise working through the courts, as servants on his first field campaign in western Virginia.”
No, later: Lee was charged with executing his father-in-law’s will, which required the freeing of his slaves. “But Lee recorded the deed of manumission on January 2, 1863, in Richmond, ’embracing all the names’ of the Arlington and Romancocke slaves, and suggesting a ‘supplementary deed embracing those who have been omitted.’ Curiously, he included among the manumissions the one enslaved family he still owned in his name, that of Nancy Ruffin.” So he owned no slaves on his own account at the time of Gettysburg. He had control over his wife’s slaves, but he also had a major stick up his ass about “honor”, and I don’t think he would have appropriated his wife’s slave to his own service.