If you are an average utilitarian, then it is better to kill yourself if you lose in quantum roulette. It increases your average utility. This is the same reasoning that makes an average utilitarian prefer to kill off the poorer members of society.

Agree, with the following clarification:

Average (or total) utilitarian preferences are analogous to preferences for many future selves but we should remember that they are not the same thing. Choosing to take an average over yourself in future everett branches is an entirely different decision to choosing to average utility of a population in one branch. (I liked the language Carl used).

Most average utilitarians will not want to commit quantum suicide*. However, "Average utilitarian-like preferences over many future selves" does seem like a good recipe for being quantum suicidal.

* Disclaimer: Being an average utilitarian in the first place is already insane. So I cannot really speak for what they prefer when things get complicated.