Roman Key-Card Blackwood

This is a convention you use to ask for aces with 4NT. What makes this convention different from the old BlackWood? The king of trump is used as the fifth ace. And you can ask for the queen of trump. This is how you bid RKCB:

4NT- 5C : 0-3 Aces
5D : 1-4 Aces
5H : 2 Aces without the queen of trump.
5S : 2 Aces + the queen of trump.

This is the standard way, and many call this convention just 0314 for the two first step. But some pair like to use 5C as showing 1/4 aces since it is more frequent. So then the response is switch, 5C shows 1/4 and 5D show 0/3.

If partner bids 5 club or 5 diamond you can ask for the queen of trump in the nearest suit that isn't the trump suit. This is how you replay:

1 step: Denies the queen of trump.
2 steps: Promise the queen of trump.

Remember that you don't have to have all aces to ask for the queen of trump. So you can't jump to 7 just because you have extra length in the trump suit.

When you partner has answered his aces or the queen of trump you could bid 5NT. For those of you who want life simple these are the answers:

5NT- 6C : 0-3 kings
6D : 1 king
6H : 2 kings

Another way to bid on 5NT is to show extra strength in a suit. 5NT promise all aces, but you are not sure about the rest. 5NT is a invitation to grand slam. 
If the responder on 5NT has a lot of extra strength (or length) he bids 7 directly. If you are in doubt just bid the suit you have extra strength. Start as low as possible. This could be a king you haven't shown or KQ combinations in a suit you have promised control in. The 5NT may also show extra strength in a suit if he still isn't sure about the grand slam.

Another tips is to reverse the to first steps on 4NT. Why? Because 1 ace is more frequently then 0 aces, and you save some space! If heart is trump you won't get the chance to ask for the queen under the 5 heart:
4NT - 5 Diamond (1-4 aces)
Now you have to use 5 spade to ask for the queen of trump, and then you are in 6 anyway, but:

4NT - 5 Club (1-4 aces)
Now you can ask with 5 diamond and pass on 5 heart!!

Well, this is free choice.... Good luck!!