I agree Saitama takes round one due to Raditz and Nappa's overconfidence, but round two is a bit tricky. I'm sure everybody knows Saitama's strength feats are insane, he's even hinted at being small moon level in the scan below. However Raditz and Nappa still have higher DC via ki blasts.
Note: this didn't even happen yet and might never happen, so don't get too excited yet.
Piccolo was equal to Raditz at this point and Nappa is several times more powerful then Raditz.
Nappa's two fingered blast also created a light sphere over a hundred thousand feet high.
The most powerful nuclear explosion doesn't even come close to creating a light sphere over fifty thousand feet high.
The point i'm getting at here is if Saitama gets blasted he doesn't stand a chance in hell based off the current feats, however i'm not saying Saitama can't win. Assuming Saitama's moon feat happens he could be taking out DBZ tiers in the future.
On a side note I've noticed DBZ has been getting a lot of hate in the battle forums recently. I know there have been problems in the past with folks saying DBZ is universe level and so on, but it's no excuse to downplay a whole series based off a few bad apples.
I'd like to thank @Dream: for letting me get my points across.