Try something like this as the body onresize event handler. In this case "divOuterCriteria" is just a separate section I have above the scheduer for the user to select filter criteria, but you get the idea.
sched = $find(
"<%= scheduler.ClientID %>"
objRef = document.getElementById(
sched.set_height(($telerik.$(document).height() - objRef.offsetHeight - 2) +
ETA - I don't have any problem with width, it adjusts automatically. Is your scheduler width set to 100%? You may need to put it in a containing HTML wrapper and let it fill that. You might play around with some of the settings like NumberOfSlots and what not, I seem to remember some of those affecting that too.