Photoshop doesn't support to apply border radius after drawing of rectangle. I found this link and tried myself but seems to be not working. Is there any step is missed or is there any other idea to apply border radius after drawing a rectangle?
Using script plugin we can add border radius in photoshop.
Here you can find the plugins.
Copy and paste plugins here "C:\Program Files\Adobe\Adobe Photoshop CS4\Presets\Scripts".
Open Photoshop file , you can run the script from File->Scripts-> Rounded_Rectangle_Radius_Resizer.