I could be mistaken, but it feels like your colleagues are not roasting someone but are taking offence at the tone of a message that whilst obviously written by someone, isn't actually from someone but is (or appears to be) an automated response.

Personally, if it was a human at the other end of a chat who started off with "Oof" I'd be fine with that as we're having dialogue, but when used as a generic automated message it would feel a little unprofessional. Not enough to complain about, but it would be noticed.

Nothing to do with bullies, personalities, or roasting someone. Quite the opposite in fact in that it is totally fine from humans - just not ideal from an automated system.