You can use this URL : http://rootsite/_api/Web/webs?$expand=Lists/RootFolder&$select=Lists/RootFolder/ServerRelativeURL
. This will return the subwebs along with the lists property expanded for each subweb. The Lists
property will return all the lists and libraries associated with the subsite. Also, the RootFolder
property expanded for the lists will have the ServerRelativeURL
for the lists which you can use.