What a great apartment! It's stylish, thoughtfully decorated and well-maintained. Roberto is an excellent host: helpful, easy to reach and welcoming.
The location is fantastic with so many great bars, restaurants and shops nearby. Roma Norte is a vibrant, hip neighborhood but more manageable than the crowded Centro Historico. It's also convenient for getting anywhere else in the area that you'd want to go. When I return to Mexico City, I will certainly look to see if this place is available.
One tip. The apartment is near a couple of hospitals, so the streetside bedroom can be a bit loud late at night when ambulances go by, so bring earplugs if you're a light sleeper.