The "check seed via roamer" method is not reliable if I only have 1 or 2 roamers out, right?
It's less helpful, but you can still use it - just tell RNGReporter which roamers you have out.
I personally only have 1 roamer out, but I'm still usually able to use it to confirm my seed with great certainty. This is because I can always get within about ±6 of my delay, so I just have to check where Entei would be for each of those seeds. As long as there are no repeats, that's enough information to check my seed (or at the very least, discover that I did not hit my seed if Entei is on the wrong route).