What do you mean similar to Roman letters?

Those are just examples. I wouldn't aim for that kind of writing, though. Get as close as you can to the fonts on computers, but be aware that there are different ways to write a radical and some hiragana or katakana.

One thing is more important than anything else, and cannot be stressed enough:
Use proper stroke order.
Use proper stroke order.
Use proper stroke order.
Use proper stroke order.
Without proper stroke order, your kanji will be illegible once you start writing them like a native.

Edit: I should clarify. Once you start writing like you do in your native language, your strokes will run together. If you follow improper stroke order, people won't be able to discern the swoops of your lines because the shapes will deviate too far from the norm. Or, at best, they will look like really ugly characters.