To Be Useful
To Be Of Use, To Be Helpful, To Be Of Service
godan verb
When you stand up to do your duty you're standing up and finally being useful. That's why this verb means to be useful.
やくにたつ
The reading for 役 is the one you learned with the kanji. The 立つ reading is that of the 立つ vocabulary, which you should be familiar with by now.
日本ごのべん強の役に立つサイトを見つけました。
I found a website that is helpful for studying Japanese.
ハンガリーには、にげるははじだが役に立つ、ということわざがあります。
In Hungary there is a proverb meaning, "Running away is a shame, but it's useful."
ゾンビがいっぱいの町を歩くなら、銃よりも剣の方が役に立つだろうか？
Would a sword be more useful than a gun for walking through a city full of zombies?