Robert C.Cowart;19;of Belle Vernon;Rostraver Township;died Monday;Feb.16;1998;at 12:15 a.m.in North Charleroi.  Born Nov.16;1978;in Memphis;Tenn.;he was the son of Rose Bonucci Cowart of Rostraver Township and William D.Cowart Sr.of Memphis;both of whom survive.  He was a senior at Belle Vernon Area High School and planned to enter the U.S.Marine Corps after graduating with the Class of 1998.  He was employed at Pizza Hut in Belle Vernon.  In addition to his parents;he is survived by two brothers;William D.Cowart Jr.and James R.Cowart;at home;two sisters;Ginger Potts of Clarksville;Tenn.;and Nina Wolfe of Brookfort;Ill.;and his maternal grandfather;Robert Bonucci of Belle Vernon.  Friends will be received Wednesday from 2 to 4 and 7 to 9 p.m.in the Ferguson Funeral Home Inc.;700 Broad Ave.;Belle Vernon.  Services will be held Thursday at 11 a.m.in the funeral home with Pastor Brian Geesaman of Mentor Road Bible Church;Elizabeth;officiating.  Interment will follow in Belle Vernon Cemetery.  If friends wish;contributions may be made on behalf of the family through the funeral home.  Arrangements are being handled by the Ferguson Funeral Home Inc.