Difference between itsu and itsugoro

Hello,

What is the difference between itsu and itsugoro?

Is itsugoro more used within a question?

Thanks!

itsu(いつ/何時) means simple "When?" or "What day/time/season?".

itsu-goro(いつごろ/いつ頃/何時ごろ) means with "about" or "around".
http://ejje.weblio.jp/content/頃

"itsugoro" is more vague expression than "itsu".
So it's often used unconsciously to not restrict partner's activities.

"Itsu" means "when." "Itsugoro" means "about when."

Asking someone "Itsu kaerimasu ka?" ("When are you going home?") is asking for a more precise answer than "Itsugoro kaerimasu ka?" ("About when are you going home?"), but both can be used pretty interchangeably. Generally, no one will worry that you need an exact time or expect you to give one when using "itsu" instead of "itsugoro," so you don't need to focus too intently on which one has been used.