To Roll
To Tumble, To Lie Down, To Be Scattered About
intransitive verb, godan verb
You know the kanji here means revolve. The verb version of this is similar. It means to roll or to tumble. You have to be revolving in order to roll or tumble, right? 転がる is intransitive, so it doesn't take a direct object. A ball rolls down a hill. A tumbleweed tumbles. No direct object, right?
Verbs ending in okurigana that rhyme with ある tend to be intransitive like this. You can remember this because if something is ある, it's just there, existing, not acting on anything else. That's why verbs that sound like it are often intransitive too!
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
What should you do when you want to roll down a hill? Become a bottle of Corona (ころ). Just imagine yourself as a bottle of Corona, rolling down a hill. You're a Corona bottle, so you roll super easily. Now feel the grass under your glass as you roll down that hill. Nice, isn't it?
ボールが転がる音がした。
There was a sound of a ball rolling.
毛虫なら、その辺りにたくさん転がってるでしょう。
For caterpillars, there are probably many lying down around there.
転がる石？イギリスのロックバンド「ザ・ローリング・ストーンズ」のことですか？
A rolling stone? Do you mean the English rock band The Rolling Stones?