Navigate to Windows-->Interactive-->Buttons
Select your Button on the document page.
In the Buttons panel , Select the "Events" :- Roll Over
and click on the "Plus" sign infront of "Actions" in the buttons panel to define the action of State change for roll over
Once done :- Change the "Event" :- On Click
and define the action "Go to Next page" as you did earlier
You can get the more info from the :-
http://www.adobe.com/support/indesign/gettingstarted/pdfs/indesign_rid _whitepaper.pdf
http://helpx.adobe.com/indesign/using/interactivity-5.html
