In Romeo and Juliet, what does the Friar say about Romeo's relationship with Rosaline?

In Act II, scene iii, Romeo visits Friar Laurence to arrange his
marriage with Juliet.  Of course, being Romeo's confessor, Friar Laurence knows that Romeo has
been, up to this moment, "in love" with Rosaline.

When Romeo shows
up so early in the morning, the Friar's first thought is that Romeo has spent the night with
Rosaline. He says, "God pardon sin.  Wast thou with Rosaline?"  And when Romeo explains that he
has been "feasting with [his] enemy," and he has fallen in love with and wants to marry Juliet,
the Friar is flabbergasted at his haste.  He says:

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Holy Saint Francis!  What a change is
here!

Is Rosaline, that thou didst love so
dear,

So soon forsaken?  Young men's love then
lies

Not truly in their hearts but in their
eyes.

Jesu Maria!  What a deal of
brine

Hath wash'd thy sallow cheeks for
Rosaline.

. . .And art thou
chang'd?

When Romeo says that Rosaline
did not return his love, the Friar comments:

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O she knew well

Thy love did
read by rote that could not
spell.

This means that Rosaline knows
that Romeo is too fickle to really care deeply for a woman yet, he isn't far enough along in his
"studies."

The Friar, despite his misgivings, decides to help Romeo
and Juliet marry secretly, hoping it will mend the feud between their
families.