You can roll for every individual characters you have for the group activity, the more characters get involved, the easier it is to find a new place with new items and den places and so on!...
You may also roll dice (if you want) even if it isn't a group activity when your characters are just hanging about, then they can spot smaller items, prey animals or interesting twigs, stones, stuff like that!... stuff that I'd love the character to interact with! (Tidemist threw 6 underwater so she found the Snapjaw and scales and stuff even as it was not a group activity, lots of stuff because six is a biggest number on the type of dice we are using! if she had thrown 1, she would not have found anything that time)...