You can go directly from Calgary to Rome via Heathrow or charles de Gaulle but it's expensive. I usually fly Calgary - Heathrow - Toulouse or Calgary- C.D.Gaulle - toulouse where my village is near.
It was my first trip to Abruzzo and I wanted to drive everywhere so I flew to Frankfurt with Air Canada, bought a cheap ticket from Ryanair to Pescara then rented a car and drove in Abruzzo, down to Rome, along the coast mediterraneen up to Genoa, returned the car there (they don't allow you to return a rented car in another country unless you pay a really high fee). I then took the train to Nice, rented another car and drove all the French riviera up to Toulouse then to my village which is an hour west of Toulouse.
When flying with Easyjet or Ryanair you always have to go to secondary airports(ie. Gatwick, Orly in Paris, Frankfurt Hann in Frankfurt) so you have to change airport, sometimes sleep overnight in hotel if your flight is not on the same day. At the end I don't know if it is cheaper! and they limit you to one suitcase only under 17kg and one carry-on.
If you fly Calgary/France, you will land in Charles de Gaulle, you have to transfer to Orly to fly to Rome on Easyjet. But if you want a couple days to enjoy Paris before going to Rome then that's the way to go.
Hope this will help.
Yvonne