- The deprecation warning is just a warning (duh). It will be gone once you put the Jest configuration in a separate file (which I recommend to not bloat your package.json).
- <rootDir> should be the root of your project by default. Make sure your tsconfig file is available on the specified path. Alternatively, you can change the path yourself: https://kulshekhar.github.io/ts-jest/user/config/tsConfig
I hope that helps.