I went to the Rose garden in Osaka city.

Hi. I went to the Rose garden in Osaka city.
It was so beautiful and the scent was so good. ( I would add the here since, you're talking about the scent that is in the Rose Garden, you'll want to use the word the)
I saw many colorful flowers. (since you're using color to describe the flowers, say colorful instead.)
There were yellow, pink, red and white. (use were instead of was since, you're listing many things)(general rule: if you have a lot of nouns, your verb shouldn't have an "s") 
I loved the deep pink rose. (Since your whole journal entry is in past tense, you should keep the whole thing in past tense)
I took a picture in front of the deep pink rose.

This skirt is LIZ LISA.
I like it.

Thank you for reading.
If you find a mistake in my notebook, could you correct it?

I went to the Rose garden in Osaka city.

Hi. I went to the Rose garden in Osaka city.
It was so beautiful and the scent was so good.
I saw many colored flowers.
There was yellow, pink, red and white.
I love the deep pink rose.
I took a picture in front of the deep pink rose.

This skirt is LIZ LISA.
I like it.

Thank you for reading.
If you find a mistake in my notebook, could you correct it?

I went to the Rose garden in Osaka city.

Hi. I went to the a Rrose garden in Osaka city.

You only need to capitalize "rose gardens" if the name of the garden itself is "rose". But if it's just a garden of roses, then it doens't need to be capital.

It was so beautiful, and the scent was so good.
I saw many colorful flowers.
There was yellow, pink, red and white.
I love the deep pink roses.
I took a picture in front of the deep pink roses.

The reason why the "s" after rose is so important is because you didn't take a picture in front of just 1 rose (一つのバラ）, you took a picture in front of many roses　(多くのバラ)!

This skirt is from LIZ LISA.
I like it.

Thank you for reading.
If you find a mistake in my notebook, could you correct it?

Mizuki, you worte so well, as always! 

It looks liek yo had a fun day! ^^ I love roses as well, I like the light pink coloured ones!

If you have any questions about my corrections, please feel free to ask!