Custom Database Roles -- Insert

I am trying to set up a Custom Database Role that allows the user to
select, update, insert and delete data. I created the role by
combining the built-in roles of db_datareader and db_datawriter.
However when I logged with the custom role I was not able to insert a
new record.

When I then went in and assigned Insert rights to the table I was
trying to insert to, I was able to do it. But if I go that route I
end up having to set permissions on every table in the database. I
just want to grant these rights to ALL the tables.

Is there a straighforward way to do this and why didn't adding
db_datawriter to the role definition accomplish this?

Thanks.

Steven

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