Correct me,
He reached final island 13 years ago.
And Roger and Oden were together for a year maybe.
then 5 year of dance.
End of oden is exact 20 years ago.
That makes it 26 years.
And 13 years ago is, 39 years ago. Same time as god valley.
Given how luffy and co advancing. I think a year is enough to cover the grandline.
So is it still hard to assume Roger started that journey after wards?