I ran across a question posted to Yahoo Answers recently that read something like "I just got an espresso machine for Christmas. What are the best beans to use"? The answer was "Any dark roast. French roast would be good".
I don't think the person who posted the answer really had a clue and expressed the common misconception that espresso roasts are dark. The fact is that French roast would be about one of the worst roasts to use for espresso. I know; I've tried them myself. You definitely won't be getting any crema out of French roast and altogether it will be a very unsatisfactory outcome and for the beginner at home something that is likely to put them off home espresso brewing completely not knowing that the wrong beans were recommended.
Actually, most of the best espresso roasts are light to mid-roast. What is known as "city roast" is a mid-roast and is the type of roast that is used for the best espresso-based drinks that come from the best coffee shops.
Dark roasts get to the point where the oils of the bean are being forced out through the outer hard shell of the coffee bean because of the extra roasting time and heat. The beans are dark, shiny, and wet looking. If that's how your beans look, then you won't be getting any crema out of them. Use them for filter coffee of French press/plunger coffee. Beans that you use for espresso, even if a darker roast, should look dry without any evidence of the oils having come to the surface of the bean during roasting.
The best option for getting beans that are perfect for making espresso at home is to buy them from a local independent roaster. This way you know they are fresh and you can ask them for a recommendation. A good way to start is to ask them which roast they use to make espresso in their cafe and give those a shot.
But a local roaster is not an option for everyone especially if you don't live in an urban area. On top of that. local roasters tend to charge quite a lot for their beans. So here's my personal recommendation for beans that taste good and work very well for creating great crema at home. And the great thing is that you can order them at Amazon so won't even have to leave home. Put them on a monthly "subscribe and save" order, and save even more. Coffee Masters Gourmet Coffee, Ethiopian Yirgacheffe, Whole Bean, 12-Ounce Bags (Pack of 4). (Note: As of November 2015 I am still using these beans as my stock beans at home. I have been getting these beans each month for almost 3 years now! That's why I can recommend them without reservation.)
Ed. Note: In early 2011 I found these fantastic beans that are excellent for making espresso coffee, great-tasting and reasonably priced at Amazon. Currently these are the only beans I am using. Give them a try yourself and see if agree: Great Value Coffee Beans Suitable for Espresso.
Espresso Coffee Snobs