Turner, 27, is a winger who has spent the last three seasons with Sheffield Eagles, where he scored 17 tries in 2015.
“Scott was one of the first players on my list of recruits,” said Rovers coach Jon Sharp.
“He has a great attitude, good skill levels and his height, athleticism and ball skills will give us an added attacking dimension next season.”
Turner himself is hoping to help Fev to win some silverware in his time at the club.
“I’m really pleased to be joining Rovers,” he said.
“Growing up in Cas I always admired Fev as a Club and knew what the team means to the fans.
“They were always winning silverware and I want to be a part of that and help them win some more.”
Snitch, 32, is a back rower who spent some time at Fev on loan from Doncaster in the latter part of the 2015 season.
“I’m really happy to be joining the club on a permanent basis,” he said.
“It was a breath of fresh air when I switched, especially moving to a side which won most of its games.
“I like the way Jon has introduced the youngsters to the first team and look forward to helping them develop.”
Jon Sharp hopes that Snitch can add some experience and steel to the Rovers forward pack.
“I thought Steve added a great deal of experience, composure and energy in the latter part of the season and contributed to the great run of wins culminating in lifting the Kingstone Press Championship Shield earlier this month,” he said.
“With just under a month until we report for training I’m happy with the way the squad is shaping up and am looking forward to getting to work with the players in pre-season.”