Fear the nice-smelling Princess!
Latios will be generated at frame 1, not 11, because Entei & Raikou are still roaming, and Latios is obviously the only one to be regenerated.I am RNG'ing for Latios in Soul Silver. I have him KO'ed and Entei and Raikou are still roaming. In which frame would Latios be generated? Still frame 11?
I have a frame of 42, how many frame advancements do I need to do?
Latios will be generated on frame 11 only if you KO'd all 3 roamers.
And for frame advancements: Target frame (42) - Entei & Raikou frame advancements (it depends on their locations the moment you saved, might be 2, or 3, or more than 3) - generated frame for Latios (1).