Are there roll control devices other than ailerons?
Yes, that will work. If the entire wing tip pivots, it simply acts as an aileron that takes up the entire chord of the wing.

Other alternatives to ailerons include:


Weight shifting. If you can shift the aircraft's center of mass left and right a significant amount, thus will cause the aircraft to roll in the same direction. This is how hang gliders turn.
Wing warping. Essentially the same thing as ailerons, but accomplished by bending or warping the wing rather than by pivoting a hinged piece of the wing. Early Wright aircraft did this, but I don't know of any modern aircraft that do. (Birds probably do this, too.) 
Roll spoilers. By deploying a spoiler on just one wing, you'll cause the aircraft to roll in the same direction. Some airliners do this some of the time. 
Sliding the wings left and right. Okay, I admit that I don't actually know of any aircraft whatsoever that do this. But if you were to slide an aircraft's wings left or right, that would cause it to roll in the opposite direction.
Cyclic pitch control. Only rotary-wing aircraft (such as helicopters) can do this. The rotor blades can be configured to change pitch depending on where they are in the cycle, and this can produce a roll. Cyclic pitch control is the main way that helicopters are controlled.
Yawing and using the dihedral effect. An aircraft doesn't actually need any roll controls at all if the wings have a significant dihedral angle. Instead, you can roll the aircraft by yawing it into a sideslip; the dihedral effect responds to the sideslip by rolling the aircraft. A lot of RC aircraft use this method, as does at least one ultralight aircraft, but it's not a great way to go, because sideslips produce drag, and they can produce a "snap roll" in the event of a stall.