Short Answer: YES
You can absolutely make a simple rounded button without the need of an additional background image or writing any code for the same. Just follow the screenshot given below, to set the runtime attributes for the button, to get the desired result.
It won't show in the Storyboard
but it will work fine when you run the project.
Note:
The 'Key Path' layer.cornerRadius
and value is 5. The value needs to be changed according to the height and width of the button. The formula for it is the height of button * 0.50. So play around the value to see the expected rounded button in the simulator or on the physical device. This procedure will look tedious when you have more than one button to be rounded in the storyboard.