In most companies there isn’t even a big difference in oncall duties. At FB, PEs (SRE equivalent) share the oncall duties with us equally. PEs focus more on systems and reliability aspects of the service.
Is there a pay difference between the two though ?
Not at FB
Different companies have different roles for the title.
Amazon has SysDev equivalent to SRE. But the work is subjective. There is no difference in my org, both SDE and SysDev does same work.