This is a shot at a blues/rock lesson. This line is based on the 12 bar I-IV-V blues progression, starting on Bb and utilizing only the roots of the chord.
A I-IV-V progression works like this:
The first four bars are based on the root. In this case, Bb.
The next two bars are based on the fourth of the root. In this case, Eb.
The next two bars go back to the root note.
The next bar is based on the fifth of the root. In this case, F.
Next, it goes back to the fourth.
The last two bars are based on the root Bb.

I hope this helps! Any suggestions or corrections, please AB mail me!