The 25-year-old former Huddersfield player, who had a brief spell in rugby union with Sale, becomes the Robins' sixth new recruit for 2013 following the capture of Evarn Tuimavave, Cory Paterson, Sean Gleeson, Travis Burns and Omari Caro.
Hull KR coach Craig Sandercock said: "I saw quite a lot of Batley this season and Alex was a stand out for them on the wing. He has good speed and is a powerful runner. Alex has some real potential and I am confident he has the ability to make the step up to Super League."
Rovers have released 20-year-old full-back Louis Sheriff to enable him to join Australian club Redcliffe Dolphins, Brisbane Broncos' feeder team who are coached by former Crusaders boss John Dixon.
Sheriff played the final six games of the season and was tipped to be the first choice full-back following Shannon McDonnell's departure.
- Cory Paterson
- Evarn Tuimavave
- Travis Burns
- Craig Sandercock