Link to heading in node?

Is there a way to link to an org (sub)heading in another node?

Yes and no.

Org-roam does not add to Org’s link syntax. ID links in Org mode only link to an ID; there is no syntactical way to link to an ID’s (sub)heading. So… This is not correct Org’s link.

[[ID:<id>::*heading-description]] 

You can use Org’s file link synax like these, but I don’t think these are not recognized as backlinks by Org-roam – you can try:

‘file:projects.org::*task title’ (headline search)
‘file:projects.org::#custom-id’ (headline search)