I had traveled to India thru Frankfurt twice last year with a valid H1 stamp on my passport. Seems like that has changed and a transit visa is required now for non-immigrant visa holders, including H1.
This is from the German consulate website in Houston, for Indian citizens:
Exception 1 to the list above:
If you hold a residence permit for a member country of the European Union or if you hold a permanent residence permit allowing unrestricted return for Andorra, Japan, Monaco, San Marino, Switzerland or the United States of America (only green cards with 10 years´ validity will qualify) you do not need an airport transit visa.
If you are still in doubt whether you need an airport transit visa, do not hesitate to call the German mission which serves your place of residence in the US.