Hi Margaret,
As I understand it, another family tree, such as in Rootsweb, or a stand-alone web site, or an Ancestry Family Tree, or a family tree in FamilySource.org, or other information on Find A Grave, are secondary sources at best. They could be correct. Or they could be incorrect. A lot depends on if there are primary sources that are attached to those other family trees.
Ideally, we would like to have links to primary source documents in WikiTree profiles. I understand, though, that when profiles are first entered in WikiTree, sometimes these secondary sources are all that is currently available. I know that sometimes that's all I have to go on in the beginning.
I would do two things: leave the references to the secondary sources on the profile, and add the {{Unsourced}} template as a notice to others that primary sources still need to be found.
If there are other primary sources that are attached to these other family trees, at least make a note of it in the WikiTree profile. I usually put a sub-bullet underneath saying that there are other sources at the link.