In our class tonight... well every night, we warm up with ukemi and taihenjutsu drills. These are so fundamental to Bujinkan training that I do them every class.
What is also fundamental is to try them ryote, katate and mute. That is: two handed, one handed, and no handed. This way you are prepared for nearly any situation requiring evasion or hitting the ground.
Two handed gives the most control. You can use the ground as your ally and "steer" your interaction with it or be steered by it. You might discover something there to aid in your counter or as metsubushi.
One handed can be necessary if one hand is otherwise occupied. Maybe you are being thrown by a joint lock on one arm. Perhaps one arm is injured. Perhaps one hand is drawing a weapon as you evade an attacker. In any case, you should know how to do this with the lead or rear hand.
No handed is the most acrobatic. This takes the most control with the legs. Often when students don't use the legs properly in their normal ukemi practice, they compensate by absorbing shock with the arms and upper body. When they first try a no handed version, it can be a bumpy ride.
The ukemi we do every class are:
zenpo kaeru kaiten
koho kaeru kaiten
and sometimes we add various tobi or aruki, breakfalls and nagare.
These can be done from any kamae. With or without weapons.
And it's fun!