This code works thansk to ESRI developer helping solve it.

var rows = $ ("#roomUseTable").jqxGrid ("getrows");

    for (var i = 0; i < rows.length; i++) {
        // if value of field 'OBJECTID' is in roomsAssignedData array
        if (roomsAssignedData.includes (rows[i].OBJECTID)) {
            // add row to selection
            $ ('#roomUseTable').jqxGrid ('selectrow', i);
        }
    }