How much is a roll of mercury dimes worth?

It depends. A coin's value is affected by its scarcity, mint mark, and it's wear.

You'd need to examine each coin, to get an idea of how worn it is, and examine it's mint mark and grade. You can then make a rough estimate of each coin's value by looking at numismatic collectors books, to see what your coins are worth.

Specifically, in the case of a Mercury dime, it will be worth between one to two dollars for its silver content -- some might be much more valuable. Whatever you do, don't sell them to a scrap metal dealer without having them evaluated first! I had a relative who did that "because it was easier," and he lost several hundred dollars on the deal! Unforgivable to the informed, collector!

So called "junk silver," all circulated, pre-1964, twentieth century US Coins (sans nickels) IE dimes, quarters, half's, and silver dollars, have both numismatic value as well as "scrap" value.

Today, (Fall 2009) a roll of Mercury Dimes is worth about 75 to 100 US dollars or less at scrap prices, as the spot price varies on a daily basis.

Some coins, may be worth more, because of their numismatic value to collectors, but generally, circulated coins, are only good for scrap prices. You never know what you have until an expert evaluates your collection. That's one of the things that makes coin collecting, so much fun.

One other thing ---Whatever else you do, DON'T try to clean the coins to make them look "nicer." Anything, you have at home, except maybe distilled water, will damage the coins and reduce their value to a collector.