Solo has been low-key questioning Roman since last year's MITB. Remember when Roman was
and kee-keeing dead to his face when the Usos initially suggested that Solo could lead the family? He can say that Roman only named him tribal heir because he thought it would keep Solo off his ass/under control -- or so he can manipulate the situation like he normally did when really, Solo's BROTHERS saw it in him before Roman did -- when really, he just dug his own grave and set the current actions into motion.
And then during the Civil War, the nikka whose supposed to be the damn leader about had a breakdown when the Usos wouldn't just lay the fukk down to where Solo had to be all "The fukk you panicking for? Get up and fukkin' finish the job!!
"
And then going back to the numerous times Solo has single-handedly saved Roman's title reign. He can even spin it where he sacrified his own success (i.e. the losing streak) because the mission was to keep Roman on top, only for Roman to fail on the biggest stage when the family (Rock) literally stacked the deck to where Roman had it all in his favor.
If they believe in continuity, callbacks and so on, Solo has PLENTY of ammo here (because Roman of today will cook him on the mic if he doesn't come with it), and he can top it off by saying that he never answered to Roman, but he answered to who sent him (The Elders, Rock being one of them), who told him to ensure Roman stayed on top until he proved he couldn't, and then take over when it was time.