In my experience, trying to abuse the RNG before fighting the elite four is an exercise in futility. That NPC screws everything up. It's possible to get it to work, but it was proving to be too much trial and error for me. For reference, the first roamer respawned does indeed respawn on frame 1, as I've tested it by starting right in front of Lance and fighting him with no frame advancements.I only have one roamer possible, entei, b/c I already caught raikou. After beating the E4, I deduced that entei respawned on frame 6. This was b/c I had 6 pokemon in my party and must have tripped the 128 step counter, and that the entei I caught and checked was at frame 12. Subtracting 6 from 12 left 6, and there was no other possible frame advancement b/c I was saved right in front of the entrance to will's room and entered as quickly as I could upon starting the game.
Unless the NPC advanced by just 1? Meaning I reached frame 12 b/c +6 from 128 steps, +1 for NPC(if it was NPC), leaving 5 for entei's starting frame? Or could it be 6 for entei's starting frame if NPC never moved.
Can anyone else confirm that roamers respawned after beating the E4 start at frame 6 or 5, rather than 1?
Since you have already caught Raikou, I recommend that you release Lati@s and then try this. It should work if you have 1 fainted roamer + 1 active roamer. You'll just start from frame 2 instead of frame 3 like the guide says.