SQL Server - An expression of non-boolean type specified in a context where a condition is expected, near 'RETURN'

That is invalid syntax. You are mixing relational expressions with scalar operators (OR). Specifically you cannot combine expr IN (select ...) OR (select ...). You probably want expr IN (select ...) OR expr IN (select ...). Using union would also work: expr IN (select... UNION select...)

An expression of non-boolean type specified in a context where a condition is expected

I also got this error when I forgot to add ON condition when specifying my join clause.

Your problem might be here:

OR
                        (
                            SELECT m.ResourceNo FROM JobMember m
                            JOIN JobTask t ON t.JobTaskNo = m.JobTaskNo
                            WHERE t.TaskManagerNo = @UserResourceNo
                            OR
                            t.AlternateTaskManagerNo = @UserResourceNo
                        )

try changing to

OR r.ResourceNo IN
                        (
                            SELECT m.ResourceNo FROM JobMember m
                            JOIN JobTask t ON t.JobTaskNo = m.JobTaskNo
                            WHERE t.TaskManagerNo = @UserResourceNo
                            OR
                            t.AlternateTaskManagerNo = @UserResourceNo
                        )