[1] Key features of Romex are the multiple meanings attributed to certain bids, such as the dynamic one notrump and the Mexican two diamonds.
The dynamic one notrump opening indicates either: The most common responses to the dynamic one notrump opening are: Higher-level responses indicate control count.
A consequence of the use of the dynamic notrump is that the 1NT rebid by opener becomes wide-range (typically 12-16 hcp).
With game invitational values or better, responder reacts to such a rebid with a 2♣ checkback convention to ask opener to further describe his hand.
Romex employs special asking bids in lieu of cuebidding, and for slam investigation.