I am not an event photographer, but like any of you I enjoy shooting events I participate in. Let me show what I use to get studio-like lighting in any regular size room (for a bigger ceilings, 30 and more feet it won’t work that good).
The main idea is to have more than one light sources: one for a model and the second one is for reflection and the rest of the room. With only one flash attached, even if used with light diffuser, you can’t have good light spread. The best you will get in a relatively large room is a flat looking model and some shadow behind.

dual dedicated flash setup for canon
Much better results will be by using 2 light sources:



