This is a tough question unique to rothschildianum given the fact that it has been intensely sibbed for 4-5 generations now (and a few prior on a lesser scale in highly skilled hands) and continues to advance in quality and garner awards at the highest level. I do not know if it is the most awarded species of all time- but if not, it surely is in the top 10.
That said, there are diminishing returns on a relative basis. Your average roth is far better than 20 years ago (in large part just for blooming on a regular basis- or at all- in the first place), but plants of the highest quality are fewer in number as the bar is set ever higher each year.
Point being- if you just want a really nice roth, then I think buying any of a number of the better crosses out there is going to give you good odds of a nice plant. But if you want good odds of a plant that is going to be award quality and suitable for cutting edge breeding- tnyr5 is correct that you are better off buying flasks and growing out the seedlings. This is not solely because it is more cost effective, but because demand for roth is so intense that for the best crosses flask size is sometimes your only opportunity to get the cross at all, and it is certainly your best chance to get plants that will be the most vigorous and promising. Once the better crosses get to a certain age, many breeders will keep all or most of the plants- certainly the most vigorous ones- for themselves. That is how it has always been. In flask stage, while plants certainly vary in size, it is still too soon to see which the real front-runners are going to be. I think that is best evident after a year in single pots, at the earliest.
As for selecting crosses just looking at the parent names and knowing nothing further- with the caveat that this is not a perfect way of doing it- the market places the highest value on parents which have won medals awarded by JOGA, followed by AOS awards. But again- this is a very fast moving world and not everyone can get a prized roth to Tokyo in perfect bloom for evaluation, or indeed the US. German breeding lines of roth are very highly regarded- but for obvious geographic reasons top clones do not often bear JOGA medals or AOS awards. So it is not uncommon for a very cutting edge cultivar to not have been awarded.
Your best bet is to find a highly respected breeder/retailer you can trust and ask them to suggest crosses based on your goals (do you want most to see a big dorsal, longer petals, reliable blooming, dark color? etc.) and then buy several plants. Ask for or select crosses that are newest to market, and buy the largest size available. Quantity is up to you, but if you really want to get an exceptional plant- then you really need 5-10 plants each of a few recent crosses to best your odds.
All IMHO- an educated opinion I like to think, but an opinion nonethless on a very good and complex question.
On specific crosses- I bought some of the $200 World Cup x Raptor plants from Orchid Inn a couple of years ago. Sold most of them but the 2 I kept bloomed with 15 inch leaf spans. Even blooming that young, the flowers were not good enough for me to keep them (for a plant that big, I want AM potential or better or a very unique quality for breeding)- but they were certainly very easy to flower and well above average qualitatively. If you can still get them- go for big plants at this point- a worthwhile cross.
The most "cutting edge" roths I have in bud right now are 'Black Eagle' x 'Knight Challenge' SM/JOGA (in a personal capacity- not in my sometimes dealer/retailer capacity), and while it was an educated guess to go for them, it is a cross now reaching flowering size I would seek out if you can find it. (And unlike the cross above, these are budded at a more customary size).
If you are willing to consider flasks and small seedlings, look for 'Giant Perfection' (not yet awarded to my knowledge) as a parent. Again- a guess on my part, but I really like the potential there. Fingers crossed.
. All jokes aside this is some really great information. I am not getting it for judging but rather for personal satisfaction. I don't really have the patience to wait for a flask to mature: Isn't it like 6-plus years till flowering? Also, I don't have the financial backing to buy tons of roths to get a perfect one. I was thinking of getting a good cross from orchid inn and hoping for the best. In your opinion would you buy multiple small plants or just go for a high end blooming size one? Also these are the crosses I'm looking at and what would you think the best one would be? 
