No, your rotation speed will most definitely vary based on takeoff weight. Ideally there would be a conversion chart published, but I haven't been able to find one.
My recommendations? Rotate at 120 if you have A2A armament and a single drop tank. If you have a drop tank and a full load of bombs, around 130-135 would be better.
If you have two drop tanks and A2A armament? I've struggled to get off the ground rotating at 145-150.
Do a test run, even at sea level on Caucasus. Try taking off with two full drop tanks and let me know what happens when you rotate at 120 xD you'll quickly find yourself dropping back towards the ground a few hundred meters after takeoff, even with full burner.