listResourceObjects returns a list, which can be manipulated with all of the XPRESS list operations.
<defvar name='myList'>
<invoke name='listResourceObjects' class='com.waveset.ui.FormUtil'>
<ref>:display.session</ref>
<!--
Your
other
arguments
go
here
-->
</invoke>
</defvar>
<dolist name='element'>
<ref>myList</ref>
<block trace='true'>
<ref>element</ref>
<!-- Add whatever operations to perform on the elements -->
</block>
</dolist>
This will output the individual elements of the list. You could just as easily put the trace around the defvar, but the dolist is where you'll do something useful with the results.
Jason