Avi12Apr2017,
The Web Services API Documentation provides information about the parameters available when using the WSAPI. It is available at:
https://eu1.rallydev.com/slm/doc/webservice/
And for your specific question, these two sections apply:
pagesizeNumber of results to display on the page. Must be greater than 0 and less than or equal to 200 for 1.x API calls or 2000 for 2.x API calls. The default is 20.
Example: pagesize=30
startThe start index for queries, which begins at 1. The default is 1.
Example: start=1
If you are not using the Toolkit available for Java, it can be a real help. Although not officially supported, it is available here:
GitHub - RallyTools/RallyRestToolkitForJava: A Java Toolkit for Accessing Rally's Webservice API
You can find all sorts of examples, questions and answers to common issues here:
Newest 'rally java' Questions - Stack Overflow
There are also a couple of GitHub repositories that have all sorts of examples:
GitHub - nmusaelian-rally/rally-java-rest-apps: allowedvalues
GitHub - markwilliams970/rally-java-rest-apps: attachment
Hope that helps.
Michael