The Doctor's Links
Roran thinks the Doctor is reckless and ignorant. Technically, the Doctor did do the thing that later resulted in the downfall of his entire species, but it's not like it was on purpose. Perhaps Roran is dealing with misplaced anger and pain. Whatever the case, the Doctor is his target of ire, and while he is not above asking the Doctor for favors, he always does it with a bitter smile. Since nothing he does will matter in the end, he may as well live long enough to see what the Doctor does next.