Coin Roll Hunting can be done for a couple reasons, the main ones being simple metal searches and looking for specific dates and errors/varieties.
For metal searching (usually silver dimes, quarters and halves or copper pennies) the search is pretty simple. Silver can be found with a simple edge view and pennies are done by date. Nickels haven't changed composition since the last century except for a few years during WW2 so nickel searching is more looking for older dates and pre-38 Buffalo or
Liberty nickels.
Pennies usually saved are Pre-1959 Wheats or Pre-1983 coppers. (1982 were made in both copper and zinc).
Dollar coins are rarely searched due to the lack of precious metal content in small dollars. Some people look for varieties or NIFC's. Large dollars are rarely seen at all and most of us hoard them regardless, even though circulated Ikes are not worth anything over face for the most part they are kept by most of us. Of course any dollar coin predating Ikes are worth at least their weight in silver.
What you want to save from roll hunting is up to you. Personally I don't do a ton of roll hunting any more, and when I do it is a box of pennies or nickels here and there and the occasional few rolls of halves. I will save any half containing silver, any NIFC half in decent condition and of course any of the occasional commemoratives that make it into a roll. Quarters and dimes I save any 64 or earlier and most of the 76 dated ones (only because I like them). I tend to save any pennies from 1982 and earlier due to copper content, I even save the Zinc 82's for the heck of it. I also save any 2009 or any "S" mint marked coins I come across just because I don't see them often.
Halves are kind of a special breed. Find rates can be high at times then you may see a prolonged dry spell. The biggest problems are that they usually have to be special ordered from your source since they are rarely kept in stock. Then you have to dump them someplace. Small quantities can be spent or CoinStar'ed but larger (full box) quantities can be hard to dump absent a cooperative bank or currency exchange. It is not unusual to get entire boxes of dumped coins from other collectors and many of us have gotten their own dumps back.
Dumping more common coins (pennies, nickels, dimes and quarters) is usually pretty easy but be sure not to overwhelm your dump locations. Spread the wealth if you can.
As others have said, don't expect to make a profit. The silver rates are so small these days that you will spend much more on time, gas and hand soap than you will make with the occasional silver find. Generating hoards is pretty simple with pennies and nickels and the find rates for these tend to be a lot higher. I have had over 10% to 15% keeper rates on pennies and close to 10% on nickels over the years. The few boxes of "silver" that I have searched have been pretty slim. I tend to be a lot more successful with checking my change and CoinStar machines.
As far as dumping in CoinStars, remember there is a close to 10% fee for cash return. You can get full return if you take it in gift cards. I usually take it in Apple iTunes gift cards since I use that for buying movies, TV shows, apps and music. There are other gift card choices, check them out and if they meet your needs it is a pretty easy way to dump.
My credit union had a coin machine and I used to use it before I moved away. My current bank will take some coin but they don't take large amounts from individual customers. Most banks have done away with customer accessible coin machines, if you find one start a small account at that bank so you can use it.
Remember the golden rule: "Don't dump where you eat". There is nothing more rude than dumping a box worth of coins and asking for a new one. Banks are under no obligation to provide or accept coins, even if you have an account. Be nice, polite and thankful when they do and when they don't. Most of the time if you get friendly with a specific teller (or better yet the teller supervisor) they can set up a regular order for boxed or bagged coin. Remember to bring a box of donuts or something once in a while to let them know you appreciate it. They remember things like that and will often save unusual coins for you. I had a head teller give me a
Morgan dollar she found and saved for me for 3 weeks because I brought her crew a box of coffee and a dozen donuts a couple months before.
One more thing: Marking searched coins is very controversial. While it can help determine if the coins have been searched it also ticks off a lot of collectors as it basically is defacing thr coin. While it may not have any value now it might in the future but that future value is now ruined when marked. If you return coins rolled you can make a mark on the roll itself without defacing the coin. I do not recommend marking searched coins.