I've tried creating separate categories for keys as well as Old World and Buring Crusade. However, I was getting an error that the addon contained invalid characters. Characters such as "-" or "_" work, but is there a place in the code I can alter to make it accept spaces?

Roster tries to detect invalid characters in the Roster URL
When you make a category with an invalid character, then it complains
Looks like a space is an invalid character

It's a small oversight on the development of this addon

The restriction is set in lib/roster.php
Line 227
It is a reg_ex expression meant to only allow certain characters
'/[^a-zA-Z0-9_-]/'
This allows only a-z 0-9 - _

I do not know how to add space as an accepted character
Just adding a space in this causes an error

Add \s to allow any whitespace, including space, tab, and newline.
Newline is invalid in URLs already though.

Thanks a ton, that fixed it!