cob & not being in a sorority first semester

Which sororities usually do COB? Which ones are most likely to do it this year? How common is it to join through COB? Will you not get a COB if you’re seen downtown partying? I dropped out of rush because I was really sick.
What are good ways to make friends first semester of freshman year? Worried that it’ll be hard because my roomies all joined sororities and I didn’t.