"The Road Not Taken" was written using a format of four stanzas. Each of the stanzas has five lines in it. When you look for rhyming words in any one of those stanzas, you will see and hear that the first, third, and fourth lines end with words that rhyme with each other.
Two roads diverged in a yellow wood...
And be one traveler, long I stood
And looked down one as far as I could
The second and fifth lines of each stanza end with words that rhyme with each other, but not with the other rhyme contained in that stanza.
And sorry I could not travel both...
To where it bent in the undergrowth;
This rhyme pattern could be described as "abaab". Different pairs of rhymes are used in each of the stanzas, but the same pattern is present in all of them.