The 31-year-old's senior debut came with Golden Lions in 2013 and a year later he featured in the Super Rugby for the Johannesburg outfit and has made over 60 appearances for them.
Van Rooyen has also played for Barbarians twice last year and now will be making his debut in the English Premiership.
Bath director of rugby Todd Blackadder is delighted to have van Rooyen's services and believes his experience in Super Rugby will be an asset to the club.
“We are really pleased to bring someone in of Jacques’ calibre in time for the new season. He’s proven himself in Super Rugby and will bring a great deal to the squad both at the set piece and with ball in hand," said Blackadder.
“We have great strength in depth at loosehead with Jacques, Lucas (Noguera) and Nathan (Catt) all competing for the number one shirt after losing Beno (Obano) to injury in May. Jacques can also play at tighthead, which adds another option over the course of a busy season of domestic and European rugby.”
Bath will face the newly promoted Bristol Bears in the opening round of the Gallagher Premiership 2018/19 season at Ashton Gate on 1st September.