ceiling joist allowable span southern california
You added below the top of the wall in the comments.  So I would lag a rim joist to the studs and use joist hangers.

Span will look like this:

2x10 @ 12oc for #2

2x8 @ 12oc or 2x10 @ 16oc for #1

2x8 @ 16oc for select

span table