Vr = rotation speed. Rotation at this speed at 'normal' rate of rotation with one engine inoperative you will lift off at Vlof and achieve V2 at screen height. With all engines operating, Vlof and the speed at screen height will be higher than with one inoperative.
Vr must meet a number of criteria, one of which its its relation to Vmu, the minimum speed at which lift off is possible. Due to the vertical component of thrust, the all-engines-operating Vmu is usually less than the one-engine-inop Vmu. In either case Vmu can be limited by one or more of three criteria:
(a) the stall AoA in ground proximity,
(b) the maximum AoA attainable on the ground due to the airplane geometry with mainwheels on the runway and the tail touching the ground, or
(c) the minimum speed at which it is possible to lift the nosewheel off the runway at forward center of gravity.
regards,
HN39