The 27-year-old flanker has enjoyed an impressive three-year stint with the Titans, making 63 appearances and establishing himself as one of the best performers outside of the top flight.
He will leave Clifton Lane at the end of the season.
"I've loved every minute of my time at Rotherham and learned a lot during my time at Clifton Lane," said Dickinson.
"The supporters have been fantastic and I appreciate all the support they have given me during my time at Rotherham. I am however really looking forward to the challenges that lay ahead and of testing myself with the step up to Premiership rugby."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.