He joins promotion-chasing Charlton from rock-bottom Yeovil, where he has been working as a coach and scout.
Roberts, who played in the 1997 FA Cup final for Middlesbrough, made his first appearance in more than six years in October when he came off the bench.
He replaced the injured Stephen Henderson at half-time in the draw at home against Swindon, conceding two late goals.
Source: BBC Sport
Source: BBC Sport