SLIPPERY ROCK, Pa. -  Chris Elliott, a three-time NCAA national tournament qualifier as a competitor at the university, was named Tuesday as the interim wrestling coach at Slippery Rock University.    The university will conduct a national search before hiring a full-time head coach.    Elliott, a graduate assistant coach at The Rock during the 2000-01 season, succeeds Steve Roberts, who served as head coach for 10 seasons and sent 10 individual wrestlers into national championship competition in the last five seasons.    Roberts, himself a former national tournament participant at The Rock, resigned as wrestling coach to accept new duties within the campus recreation department.    Elliott had a 106-52 career record in four seasons as a Rock wrestler and holds the SRU career pins record with 50. He is a graduate of Kennedy Christian High School in nearby Hermitage, where he compiled a 99-12 career record as a competitor.