hiragana and katakana are far different from the alphabet when it comes to describing sound. They are actually moraic writing systems (the mora being a phonological unit under but distinct from a syllable), but since 90% of syllables in Japanese can be described by a single kana character, most people take the easy route and simply refer to them as syllabaries.
What this means, is that almost all kana correspond to a single syllable, as opposed to a single segment (sound). This means that they all are pronounced as either a vowel (あ, い, う, え, and お) or consonants followed by a vowel (almost all of the other characters). Many words serve as simple examples of this structure: つばさ has three syllables, and three characters "tsu・ba・sa" Although it's by no means proof that hiragana is a syllabary (as it certainly isn't), it's easy to think about it this way in order to help get used to the written language for now.
and yeah, ロオリ is kind of ridiculous. the イ in James can help express the dipthong in the true pronunciation of the name. Writing ロオリ is like writing ジェエムス, incorrect. Part of the problem of this is that it changes the syllable quality; it potentially inserts a syllable boundary in the middle of the long vowel, which could alter the pronunciation and pitch position in the word. In other words, it gums up the works. There's nothing bad about being wrong, but just being too stubborn to do something about it...