From your description it does not sound like this is a bearing wall, having said that don't go rip it out just yet...
When you say "rafter directly above nailed to the toplate" is it safe to assume you mean a "joist" nailed to your top plate?
Rafters run on an angle and support your roof deck.
Joists run horizontally and support your ceiling, attic.
If the wall is running parallel to the joist and is located underneath it the only load on the wall is probably incidental.
Typicaly ranchers and cape cods are constructed with either a load bearing block wall or I-beam running down the center of the basement directly underneath the ridgeline of the roof.
On the first floor a bearing wall runs down the center of the house on top of that support structure and again directly under the ridgeline.
The joists on each floor of the house run from an exterior wall, perpendicular to the roof ridge/center support wall and sit on the center support wall.
Here's a quick drawing:
In this type of scenario if there were an interior wall located underneath either of those ceiling joists and running in the same direction it should not be a bearing wall.
On the other hand there could be some unusual circumstance that would be transfering roof load onto the joist. You would see some type of vertical or angled framing member running from a rafter or the ridge pole(if there is one) down onto the joist.