There are conference rooms in the NS International Lounges on Amsterdam Centraal, Schiphol Airport and Rotterdam Centraal stations. You can reserve a conference room by contacting the relevant location by email or phone:
Amsterdam Centraal: amsterdam.central@regus.com or 088 671 1056
Schiphol Airport: schiphol.central@regus.com or 088 671 1098
Rotterdam Centraal: rotterdam.central@regus.com or 088 671 2521