Are there silver Roosevelt dimes or Jefferson nickels and if so what years and are they worth anything?
All US dimes, quarters, and half dollars dated 1964 or earlier are 90% silver and at silver prices from 06/2008 are worth at least 12X their face value. Depending on the date and mint mark, they could also be worth more than that as a collectible. You have to know those specific details before an exact value can be determined.
Kennedy halves from 1965 through 1970 are 40% silver and worth about $3 apiece. Nickels minted from October 1942 through 1945 are 35% silver and worth about 60 cents for the silver in them. They can easily be spotted by the large mintmark over the dome of Monticello. Some proof and special uncirculated sets have been minted on 90% or 40% planchets since 1964, but you will not find them in your pocket change and they are (almost) always worth more as collectibles than as silver bullion.