Oh, I've always liked to do some volunteer voice acting.
I have a variety of voices that could work for whatever characters the leader(s) of this project could consider most fitting. I don't really know much about the story of Undertale, but I would be interested in filling a part in the script, if just to try it all out.
I could privately send off a little online recording, reading off a generic couple lines in different voices and see which ones the project leader(s) like(s), if that's alright?
EDIT: Here is sample of my acting skill, capturing the essence of Mettaton as just one example:
https://vocaroo.com/i/s1Nc53Ik1Bgj
Otherwise, good luck to everyone.