Found the following and you will have to either get their service records on microfilm from the National Archives via interlibrary loan or through your local Family HIstory center in order to determine which, if any, of these men might be your ancestor.
1. William Royal, private, 1 Regt. (Yancey's) VA Militia Roll box 180 Roll exct 602
2.William royal sergeant 6 Regt (Sharp's) VA Militia Roll Box 180 Roll exct 602
3.William Royal sergeant 98 Regt (Green's) VA Militia Roll box 180 Roll exct 602
4. William Royall sword master 1 Regt Cav ( Holcomb's) VA Militis Roll box 180 Roll exct 602
Source Information: Direct Data Capture, comp.. War of 1812 Service Records [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 1999. Original data: National Archives and Records Administration. Index to the Compiled Military Service Records for the Volunteer Soldiers Who Served During the War of 1812. Washington, D.C.: National Archives and Records Administration. M602, 234 rolls