App crashing on launch in iPhone x?

You have to add font extension also Ex. roboto.ttf

In my opinion it's not specifically iPhone x simulator problem, you can run it on other simulators or real device to be sure about it.

you can find the step by step adding font to the Xcode project in this thread

Step 1: Include your fonts in your XCode project

Step 2: Make sure that they’re included in the target

Step 3: Double check that your fonts are included as Resources in your bundle

Step 4: Include your iOS custom fonts in your application plist

Step 5: Find the name of the font

Step 6: Use UIFont and specify the name of the fontand also make sure that you've added the phone to the bundle resources:

Bundle Resources:

there is also another possibility of crash because of the font which is the incorrect font name in the code (if you used it programmatically). check the font name from UIFont.familyNames

Thanks to all for thier answers & helping me. Below are some points I would like to mention:

1. It was not a font issue for me.
2. It not a permission issue for me.

The library which I used is known as "ROLLBAR" was causing app to crash. When I removed the code for this library, I am able to run my app on iPhone X.