We pronounce 'r' in Portuguese as 'h' in english words.
For example: the word 'mice' in Portuguese is 'rato' which we pronounce as if it was 'hato'. Similar to 'hat', 'hate' or 'hit'.
But never as the english word 'rat'. For us it sounds like 'rrrrrrrat', because the 'r' is too long in the pronunciation.
Summarizing: Portuguese don't use long 'r' phonemes when the word starts with 'r'. We usually pronounce as if the word starts with 'h' in english.
The long 'r' is used when 'r' or 'rr' appears in the middle of the words.
Actually, I am familiar with a rolling r such as in English 'rat', used in place of the the initial R or double RR, in rural central and northern Portugal.
But never as the english word 'rat'. For us it sounds like 'rrrrrrrat', because the 'r' is too long in the pronunciation.
Summarizing: Portuguese don't use long 'r' phonemes when the word starts with 'r'. We usually pronounce as if the word starts with 'h' in english.
The long 'r' is used when 'r' or 'rr' appears in the middle of the words.