Oh dear. It turns out I thought MoR referenced Francis Bacon, not Roger Bacon... Francis was just so much more available as a "great person from the history of rationality and science" that I must have kept misreading the name every time. I had to check Wikipedia just now to make sure I knew who Roger Bacon even was!
Thanks for correcting me, then.
It does seem a bit odd why Harry would attach such importance to Roger Bacon, compared with someone like Francis.
It might be the extra cool-factor of Roger being farther back in history (died about 700 years before Harry Potter went to Hogwarts) than Sir Francis (about 360 years).
Eliezer says (emphasis mine):
Roger Bacon lived in the 13th century and is credited as one of the earliest advocates of the scientific method. Giving a scientist his experimental diary is sort of like giving a writer the pen, not of Shakespeare, but of someone who helped invent writing.
Here's another installment of rationality quotes. The usual rules apply: