Thank you for writing.
You can execute the following line of code each time you add text to the RadTextBox and it will scroll the control to the last visible row of text:
I would like to remind you that you are not entitled to using our support services. In case you want to receive further support from us, please ask the purchase holder to add you as a license developer to the purchase.
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.