At the moment it is exceedingly difficult to get custom data from the Vert.x side to the JAX-RS side.
There is no reliable, accessible context store that can have things assigned to it on the Vert.x side that can then be accessed on the JAX-RS side.
This is exacerbated by the need by the JAX-RS side to access the message body, which means that the actual processing on the JAX-RS side is usually on a different thread from that which received the request on the vertx side.

Currently there are a few things added to the ResteasyContext, but non of them are both per-request and capable of storing more information:
                ResteasyContext.pushContext(SecurityContext.class, securityContext);
                ResteasyContext.pushContext(Context.class, context);
                ResteasyContext.pushContext(HttpServerRequest.class, req);
                ResteasyContext.pushContext(HttpServerResponse.class, resp);
                ResteasyContext.pushContext(Vertx.class, context.owner());

Unfortunately it's not trivial to add the RoutingContext because RequestDispatcher.service is called from VertxRequestHandler.handle but VertxRequestHandler is a Handler<HttpServerRequest> and doesn't have direct access to RoutingContext.