some roundabout guidelines:

Please make sure they are counter-clockwise.
In Potlatch there’s an icon that shows its direction.

No need to add oneway=yes.

The roundabout should have its own name, it should not have the name of a crossing way.
If the roundabout doesn’t have a name, leave it nameless.

The classification of the roundabout way should be like the highest of the crossing ways.
e.g. if a “primary” and “tertiary” meet in a roundabout, then the roundabout should be “primary”

See a good example here:
This roundabout has its own name, doesn’t specify oneway=yes, and is a tertiary (and not residential)

See the wiki here:

I was reading somewhere that its recommended to use oneway=yes for a roundabout.
And you can see at tagwatch that its VERY common.

So, the standard changed
Thank you for pointing to this.

Try this for checking bad roundablouts

Data from cloudmade 05.05.2009

I checked the most of them and they should be ok now.

Will there be one day a newer version so we can keep track of those errors ?