Hi Paola,
we are under the same VO, Rome. Having an interview is a matter of luck. They might call you, they might not. Unless they have specific questions about some of your documents, in that case they are more likely to call you in.
If they call you it will be after VO receives your app and most likely before they request for medical.
The interview takes place at the embassy of your country, they won't ask you to go to Rome.
If you want to prepare here is a good link in this forum:
http://www.canadavisa.com/canada-immigration-discussion-board/prepare-an-interview-t3109.0.htmlI don't know about your husband. This a senior member will know to tell you.