Who thinks it would be a good idea to collect Roosevelt dimes and junk silver do to all of the melting? Or is junk silver only good for investment for the melt?
It's generally only good for the melt. However, it is fairly easy to assemble a "short set" of silver roosevelt dimes from 1946 to 1964 that might add a little value for some collectors.
A set of circulated 1946 to 64 dimes is worth about $60. More than one commentary advises that 90% silver coins are a good way to own silver.
The folder will impress the kids someday. A few dimes might be one of the best items you could pass on to your family someday - for example on a special birthday. Coin collecting is a special hobby. It should be passed on. I have a little neighbor that is big on coin collecting. His parent's had not realized how much he was into it either. For an 11 year old I was pretty impressed with his understanding of history as it's tied to a few of his coins. (mostly pocket change, but the kid has a lot of pride to admire). I gifted him a blue book when he moved back to town fulltime again. The little fellow was real appreciative. He really went wild over a 1960's proof nickel. I only paid .50 cents for it, but it went over like a $50.00 bill. So about your junk question. By all means. I like the dimes, (Barbers and Mercury best). I have mostly Wash. quarters since that was where I was able to get the best price and availability at the time of purchase. Don't be so focused on price that you forget about availability risks.
I love junk silver. I sometimes look at my boxes of rolled up silver coins and think about simpler times. I still actively pull and roll search. I have thought about selling a few times but knowing that these coins will be melted I just can't do it. I would probably sell them to a silver hoarder or survialist but not a dealer.
I don't think coin dealers send them in to be melted. Then they'd have to pay postage. They probably wouldn't get anything but spot price at best. They could put those junk silver coins in a coin bag and sell them for a premium to someone who come in their shop and asks for junk silver. There is more profit to be made reselling them then sending them in to be melted down. Consider this....if every dealer sent junk silver coins in to be melted down, there wouldn't be hardly any left, as it's been 45 years now, and then they wouldn't be considered "junk" silver.