US-Japan-ROK Trilateral Cooperation ActThis bill requires the Department of State to seek to enter negotiations with the governments of Japan and South Korea with the goal of establishing regular trilateral meetings (referred to as the US-Japan-ROK Inter-Parliamentary Dialogue) to facilitate closer cooperation on shared interests and values.The bill sets forth membership requirements for a group representing the United States in such meetings. The group must be composed of not more than eight Members of Congress appointed by congressional leaders to serve for a term of two years.The bill also sets forth guidance and requirements for meeting frequency and location, group leadership, gifts and donations, expenditures, and reports.