I have created a small program that demonstrates using an ANTLR lexer with RSTA. A zip file is available at http://share.plaidflannel.com/ANTLR_RSTA_Demo.zip
The distribution file includes source code for the demo main program (ANTLR_RSTA_Demo.java), the interface between an ANTLR lexer and RSyntaxTextArea (ANTLRTokenMaker.java), the ANTLR grammar and lexer (DemoLexer.g and DemoLexer.java), a syntax scheme (DemoSyntaxScheme.java), and the javadoc documentation for the classes (doc/index.html).
The most significant piece of this demo is the method "getTokenList()" in ANTLRTokenMaker.java. The javadoc for that class describes the translation from ANTLR tokens to JFlex/RSTA tokens.
There is no executable jar file for this program to avoid the complexities of redistributing the required libraries for ANTLR and RSyntaxTextArea.