Really just looking at T!mmy's Pro and Con list, a great deal can be seen about this matchup. Perhaps the most evident point is that Kirby's only real match up advantage is in his ability to KO, which can be very difficult to take advantage of since ROB is more difficult to combo. ROB's floatiness seems to nullify Kirby's primary asset of being able to combo (although Kirby still can "combo," but it is more commonly the result of player-to-player reading, and is therefore not a viable argument for matchups).
ROB, on the other hand, beats Kirby from a distance hands down (even if Kirby has the lazer) and can provide Kirby with a major challenge up close. I mention Kirby having the lazer because even though it gives Kirby a projectile, ROB still has the Gyro that he can use against Kirby should Kirby ever land (which he most certainly has to do). Having the lazer improves Kirby's matchup against ROB, but not enough to even push it into Kirby's favor.
If Kirby has any hope of winning this match, he has to approach because he has no way to damage ROB from a distance. Even if Kirby gets ROB's lazer, rest assured, skilled ROB mains will know how to use ROB's lazer than will skilled Kirby mains (unless, of course, those Kirby mains main ROB). Overall, this matchup is slanted in ROB's favor. Perhaps a 60:40 ratio, ROB's favor, is reasonable?