Here is what I came up with using SW 2012
We want to use the Flex command.
I am not sure where this button is so in the upper right corner of the screen there is a search area, just start typing the word flex and you will see the icon appear.
Click on it
Now on the left side of the screen we can see the Flex menu.
I selected the top face of the watch band. (fillet2) You may need to play around with this to get the desired results.
Just looking at the picture provided I thought 345 degrees looked about right.
click the green check and save.
I am not sure what happened to the side faces. comments on that are welcomed but I hope this helps and is what you were looking for.