The REST API used for getting list view records is /services/data/v35.0/sobjects/Task/listviews/<listViewId>/results. This API always gives first 25 records for the given listview id and the limit cannot be increased.

For rest of the objects like Account, Contact etc, it can be done through custom webservice using following approach: Get the query from the following API: /services/data/v35.0/sobjects/Account/listviews/<listViewId>/describe and then use the same query to fetch data. 

But in case of Task object, describe call i.e. /services/data/v35.0/sobjects/Task/listviews/<listViewId>/describe is not allowed. It gives the following error:
sObject type 'Activity' is not supported in describeSoqlListViews 

Is there any way to get all the records of Task ListViews?