Yeah, given that burny is right up there with shooty and choppy on the list of things orks love, they'd definitely have a fighting chance at this.
I mean, I can see a Power-Klaw'd nob ripping up an Ultralisk pretty easily, since Power Klaws are essentially lightsaber hands. Lightsaber hands on huge, incredibly strong melee specialists, backed up by flamethrowers and Flash Gitz seems like a winning combination; although admittedly I'm not sure how many Boyz can cram into a Rok, so the Zerg might have it just on the numbers game.
I feel like the "Zerg scourge means always air superiority" is overstated, since that's never true in the games, even when you're invading char.
Well, it's more combined with Devourers, and this is entirely contingent on this being a Rok only invasion.
No Kroozers or it's a sweep. A lance fire sweep as hellfire rains down from space in quantities starcraft has never seen or thought of.