If you want a cushy 9-5 job, go work for a code factory like HCL, TCS and whatnot. That way you can build crap and wash your hands after handling it to the customer.
In a startup environment, you gotta build your shit and maintain it to. It's an environment that's not for everyone.
I've been in oncall roosters several times in the past. And it made freaking sure we wrote the best software we could.
I also have been on the management side of it, and the way I set it up is that whoever was the oncall engineer, if he had to work for more than 2 hours after normal working hours, he would get an additional PTO day. It actually worked quite well.