Ross will join the Paris club on December 1.
Bulls coach Frans Ludeke admitted it was a setback losing a former captain and versatile loose forward, but pointed to the huge stock of talented players that would still be available to the Pretoria outfit in 2015.
“Jono provided leadership and played at six, seven and eight for us when our loose forward department was depleted due to injuries, but thanks to our junior structures, the return of injured players and some new signings we have a strong group for next year,” Ludeke said.
“We have seen the likes of Jacques du Plessis, Roelof Smit and Janse van Rensburg breaking into the senior ranks despite being juniors, while Lappies Labuschagne also joined from the Cheetahs.
“With Springboks Pierre Spies and Arno Botha also returning to action and some proven players already on our books, we will have a very competitive group among our loose forwards,” Ludeke said.
Ross made his senior debut for the Bulls in 2011, before moving to English side Saracens for one season, where he only managed a handful of appearances.
In 2013, he returned to the Blue Bulls and made several appearances during the 2013 Super Rugby competition.
At the end of that season, Ross signed a contract extension to tie him to the Blue Bulls until October 2016, but caught the eye of the Parisian club, prompting a move.