I pulled some numbers from the Chrysler website...
Some don't make any since though...

Roadsters with autos are 3,174 lbs.
Roadsters with manuals are 3,040 lbs.
So there is a 134 lbs difference.

Coupes with autos are 3084 lbs.
Coupes with manuals are 3061 lbs.???
This 23 lbs difference. It doesn't seem right for manuals according to the above numbers

SRT-6 roadster is 3,328 lbs.
SRT-6 coupe is 3,240 lbs.

So, there is a 88 lbs difference on the SRT's vs 90 lbs on reg Crossfires between coupe and roadsters.

But...who knows why the numbers very so much between auto and manual...