to ask whether you can roast a piece of steak from frozen?

[Dhapeer]

Or do I need it to defrost?

Defrost.

Defrost (in the microwave if you have to)

Meat should be at room temperature before you start cooking it so even if not frozen you should get it out of the fridge an hour before you cook it.

defrost! run it under the cold tap for 10+ minutes

You can if you are slicing it up to do in a stir fry....