From my experience, so your mileage may vary, but nothing special is required. We created two new app servers on two new servers and installed and configured the Task Agents. They poll the db to see if there are any tasks to process, and if so, it is passed to IIS to process. You can monitor the Ice.SysRptLst to see which server processed which task and I believe the processing duration.
SELECT HostComputer, RptDescription, COUNT(SysTaskNum) AS Reports, AVG(DATEDIFF(s,CreatedOn,LastActionOn)) AS AvgDuration FROM Ice.SysRptLst GROUP BY HostComputer, RptDescription
There is a lot more information on this thread as well:
One last thing, you can also use a load balancing IIS extension called ARR, to route the messages between app servers if needed Application Request Routing : The Official Microsoft IIS Site