Roberts, 32 in September, was designated for assignment earlier today in what was a procedural move to clear space on Arizona's 40-man roster. The right-handed hitter owns a .250/.330/.398 career batting line in 1,288 plate appearances, most of which came with the Snakes. He enjoyed a breakout campaign in 2011, when he mashed 19 homers and became something of a cult hero for his all-out style of play and trademark tattoos.
Bortnick, 25, was a 16th-round pick of the Rays in 2009 and has posted a career minor league batting line of .289/.396/.431 in 1,773 plate appearances, none above the Double-A level.
Roberts, meanwhile, will be under the Rays' control through 2015.