R-OLL (Recognition before OLL) is a technique which allows to anticipate the PLL type before OLL. There are 3 PLL types:

A-Type : all corners are solved ( U, Z and H PLL)
B-Type : 2 adjacent corners to swap ( A, J, G, F, T and R PLL)
C-Type : 2 diagonally corners to swap ( N, V, Y and E PLL)

    First, lets introduce the opposite corner scheme notion. Here is a page of all schemes I use.

    The thing that makes me create the R-OLL method was the fact that I place all my B-Type PLL with the 2 solved corners on the L face, so knowing which PLL type I'll get and, in case of B-Type, knowing where the 2 solved corners will be an advantage to recognize PLL. For B-Types, it allows to recognize the PLL while Adjusting the U Face. So the goal of this method is to delete the delay between OLL and PLL.

    Now listen to the most important rule of R-OLL : the choice of "opposite corner scheme" wasn't due to hazard, For every alg you use :
*If a corner scheme leads to an A-Type, its opposite leads to a C-Type.
*If a corner scheme leads to a B-Type with 2 solved corners on L face, its opposite leads to a B-Type with 2 solved corners on R(The opposite face of L).
*If a corner scheme leads to a B-Type with 2 solved corners on F face, its opposite leads to a B-Type with 2 solved corners on B(The opposite face of F).


    There are 3 methods related to this tip : a simple , an intermediate and a complex one.
*The simple one needs 1 scheme to be learnt and allows to anticipate the PLL type.
*The intermediate one needs 2 schemes to be learnt, it allows to anticipate the PLL type and in case of B-Type to know if the 2 solved corners will be on R/L or F/B faces.
*The complex one needs 3 schemes to be learnt, it allows to anticipate the PLL type and in case of B-Type to know where will be the 2 solved corners.

    ***The easy one is...simple. The idea is to know which corner scheme gives you an A-Type. Knowing that, the opposite corner scheme will give you a C-Type, and all other schemes will give you a B-Type.

    ***The intermediate is an improvement of the simple one, just know which corner scheme gives you an A-Type and which couple of ones gives a B-Type with 2 solved corners on R or L face. The opposite corner scheme of the one which leads to an A-Type will lead to a C-Type, the corner schemes of the couple you learnt will lead to a B-Type PLL with 2 solved corners on R or L faces, and the 2 other schemes will lead to a B-Type PLL with 2 solved corners on B or F faces. Then you'll know exaclty where to look in order to decrease your recognition time.
      ***The complex way to use R-OLL is to know which PLL type you'll get for every corner scheme, so you have to know the position of the 2 solved corners for every scheme corresponding to a B-Type PLL(4 Cases). Learn one scheme for every couple of corners schemes(the 3 couples are given in the 3 columns of the examples page's boards), you'll know to distinguish all cases according to opposite corner schemes.
   

    The reason why there is no complete set of color schemes for that tip is that it depends of the algorithm you use, but there is a way to see what color schemes fits with your algs. Just do the inversed alg of your OLL and write what is the color scheme. To explore the complex R-OLL, do a B-Type PLL and place the 2 solved corners on L, B, R or F face before doing the inversed alg of your OLL, then learn the corresponding schemes!!!