How does Brabantio’s attitude toward Roderigo change in the course of Act I, Scene I of Othello?

At the start, Brabantio is really not very pleased to be roused from his bed, and even less pleased to see Roderigo. Brabantio asks who is calling to him, and here's what happens:

RODERIGO:
My name is Roderigo.

BRABANTIO:
The worser welcome.
I have charged thee not to haunt about my doors:
In honest plainness thou hast heard me say
My daughter is not for thee...

But, panicking once he realises that Desdemona and Othello have run off together, he eventually starts to rely on Roderigo to advise him and confirm his thoughts and fears:

Are there not charms
By which the property of youth and maidhood
May be abused? Have you not read, Roderigo,
Of some such thing?

And, right at the end, you see the real change. The scene ends with Brabantio saying

Get weapons, ho!
And raise some special officers of night.—
On, good Roderigo,—I'll deserve your pains.

From the "worser welcome" to "good Roderigo". In one scene. There's the change!