This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
What you have done is create a tld with the uri="DiceRoller" the only method defined in the tld is 'RollDiceTLD'
you have mapped the prefix 'mine' to the uri 'DiceRoller' therefore in your page the only tag you can call from the page with the prefix of mine is RollDiceTLD
to be able to call forEach you will need to either 1) add a new <%@ taglib prefix='somthing_other_than_mine' uri='uri_for_forEach'%> (the uri escapes me at the moment but I know it is in HFSJ OR 2) change <%@ taglib prefix='mine' uri='correct_uri_for_forEach'%>