Well, it looks like you bought yourself a Red Box to get started with and there's nothing wrong with that. Most dice rolling is determined by the rules (making an attack, doing damage, using a skill, etc) but for things that aren't covered the rolling of dice becomes entirely up to the DM.
Let's say that someone in the group has wrote into their character background that they were a blacksmith. Now, in 4th edition, all of that kind of job/profession shit is strictly outside of the rules. There aren't rules any longer for crafting a pair of shoes or a bow or banging out your own sword with how long it takes and what it costs and all that minutia. It doesn't mean that a character can't have or do those kinds of things. It's just that what exactly such a background means is up to you. If the party ends up discovering an ancient, rune inscribed anvil while adventuring and the guy with blacksmithing is all like "OOH OOH I'M A BLACKSMITH I INSPECT THE ANVIL" and then looks at you than it's a fine time to have him roll a 20 sider (maybe with a bonus from a stat thrown in). I use dice to determine who monsters attack when there's no reason for them to choose one target over another, dice to determine whether or not the party rests without interruption, dice to disguise an outcome I've already decided, dice to mess with the players (wait, you are doing what again? *roll roll roll* ok, go ahead), and sometimes I just roll dice to roll dice. They can do anything and nothing. That's what the screen is for.
