Jones, the former Harlequins, Warriors and Wales prop, will take over as scrum coach while Vesty joins the club from Bath as the new academy transition manager.
Ryan, who has already appointed Simon Cross as defence coach, said: "I want Worcester to be creating and developing the next generation of talented young coaches, and see that as vitally important to the future of the club."
He added: "Both Sam and Ceri are taking their first steps into coaching and are eager to make a positive impression. They have lots of experience to pass on and I know both will work tirelessly for the Warriors."
Jones, 36, joined Worcester in 2011 but was forced to retire from playing after suffering a serious Achilles injury against Saracens last season.
Vesty, who was capped by England under Martin Johnson, tweeted: "Unfortunately the game got faster and I got slower. I look forward to getting into the new chapter of my life.
"Thanks Worcester and Dean for the opportunity."