This is my own opinion and not every method works for each person (otherwise we wouldn't have so many methods).
I have been asked to provide romaji to some posts and words. I will refuse this (this is also why I've created a cheat sheet) and please don't ask again. I know, I sound nasty when I say it like that, but I do mean it.
Let me explain.
Hiragana and katakana are the minimum amount of Japanese kana you should know. I even think it should be the FIRST thing you should start learning when you're studying Japanese. Why? Because it is how Japanese works. We learned the alphabet when we were young, we learned the alphabet so we could read and learn more words. Kana are the Japanese alphabet, romaji is not.
A name I came across a couple of years ago was You. It's a word we know in English and on a first read we could assume it is pronounced the same. It isn't though.
Hiragana would be: よう
う is used in Japanese to make the O sound longer, so what it phonetically actually reads is yoo.
Let's see, there are even more version of it since there isn't 1 set romaji standard.
Depending on the set or the person You could be romanised as yoo, yo, yō, you, yô, yoh.
That is 6 ways of writing 1 simple word. And remember the post on kanji? Remember the 4 out of the 100+ kanji I showed that all had ひ as a reading? Yeah, that little thing about homonyms (words that sound the same). As you can see there are 6 ways to just write one combination of 2 kana. Though in some cases people use the combination よお (yoo) somewhere, that would be written in romaji in 5 out of 6 ways that you write よう(you).
So, how would you know what word it was in romaji? What spelling the actual word has in kana? You don't. Unless you use kana you can't see the intrigues of the Japanese language, simply because you can't see the actual kana and kanji involved in the language.
For the cheat sheet I used a sort of standardised version that most people use of Hepburn romaji, which is based on the English language and which is why some of the sounds are slightly different (si is shi and things like that).
Japanese language doesn't have combined vowels. They use conventions to show longer and shorter vowels (doubling and ou to show oo and ei to show ee) but every other combination is 2 different vowels (ai = a-i, oe = o-e). This is a huge difference between most western languages and Japanese. Japanese have 5 vowel sounds, A, I, U, E, O, all the sounds in the language are made up of one of those plus a consonant (with exception of N).
When you don't have much experience yet with Japanese it is too easy to actually fall into the habit of using the multi letter vowel sounds, which don't exist.
By using romaji you're not properly representing the Japanese language, you're butchering it into something that looks like English but is supposed to be Japanese.
I believe that the first thing you have to learn is hiragana and katakana, without these kana it is a lot harder to ever understand how Japanese works because you're missing a huge part of the language. Plus it is too easy to become lazy and not properly pay attention to such a beautiful language.
The other reason why I mostly only use kanji+hiragana/katakana is because otherwise the Japanese column in my trilingual posts would become very big in comparison to the English and Dutch column and it's easier if I don't have to constantly think about romanisation of words.
In the next few weeks I'll be uploading a post each week which talks about hiragana and katakana and guides you through learning the two kana sets.
Remember, romaji might seem easy in the beginning but in the end it will only hold you back since you'll never properly learn the language and the longer you stay away from learning hiragana and katakana the worse off you'll be.