Dutch-born Cukur has impressed in the Hornets' under-23 side since joining the club in January, with the next stage of his development seeing him head out on loan.
Cukur is a product of the Feyenoord Academy and also spent time with AZ Alkmaar prior to heading to the UK.
The 6ft 3in forward has become Rovers' seventh new signing of the summer and could be involved in the pre-season friendly at Wakefield AFC on Tuesday night.
Cukur said: I’m absolutely buzzing to start here and meet all the players - I feel like it’s going to be a good season.
"I had a couple of other options, but when this club came in, it just felt right.
"It’s a good club and I’ve watched a couple of games and spoken to the manager about how the team want to play and it makes it the best option for me.
"The manager played a big part in me coming here. I spoke to him, and he gave me the right feeling about coming here.
"I feel like I’ll fit well into this team and the style of play.
On his new arrival, Rovers manager Richie Wellens commented: "I think he can play as a 10, as an out-an-out forward, or off the left, so he gives us options.
"He’s got good feet but can score from crosses. He’s a talented boy and we can’t wait to start working with him.
"Even though he’s young, he’ll bring physicality. We’ve looked at him and everyone we’ve spoken to speaks very highly of him.
"We think we’ve got a rough diamond and we’ll be able to bring the best out of him.
"We’ve got him through the door, and I’m really excited about him."
Cukur's arrival follows on from the earlier captures of Ben Close, Kyle Knoyle, Tommy Rowe, Ro-Shaun Williams, Jordy Hiwula and loanee Matt Smith.