At Boxmeer Station take bus number 84 to Gennep.
From here you will need to call the call-a-bus service 21 (call 0900-0699 an hour in advance) to take you to Maria Roepaan, Gennep.
You can also take bus 83 from Nijmegen station to Gennep and there change over to call-up bus 21.
Or you can bus 83 direct from Nijmegen station to Heijen. From both Gennep and Heijen it is a walk of more than 20 minutes.
The closest airports to the park are Weeze (DE, 30 km), Eindhoven Airport (NL, 65 km) and Amsterdam Schiphol (NL, 145 km).