The 4th pattern B Major scale takes it’s root note positions from the E shape open chord. When looking at the open E chord, the root notes are on the open Top and Bottom E strings and the 2nd fret D string.
E
Important: The notes used in the B Major scale are B, C#, D#, E, F#, G#, A#, there are five sharps in the B Major scale.
If we take a look at the scale on the fretboard, you will see something like the following pattern… the root notes are marked with the “X“
| $1.6.$3.6.$4.6.$5.6.$6.6 | $1.X.$2.7.$5.7.$6.X | $3.8.$4.8 | $1.9.$2.9.$3.9.$4.X.$5.9.$6.9 |
Note: In the diagram above it’s the fret numbers that are indicated not the scale degrees, and it isn’t the way you would normally write out a scale using TAB, it’s just to illustrate the fingering pattern of the scale. 
When playing this scale on the guitar, I normally start on the lowest pitch root note, the 7th fret E string with the middle finger, and play up to the highest pitch note of the scale, 1st string 9th fret, which is a C# note.
| $6.7 9 $5.6 7 9 $4.6 8 9 $3.6 8 9 $2.7 9 $1.6 7 9 |
Descending back to the lowest pitch note of the scale, the A# on the 6th fret bottom E string.
| $1.9 7 6 $2.9 7 $3.9 8 6 $4.9 8 6 $5.9 7 6 $6.9 7 6 |
Then back up in pitch to the B root note on the 7th fret bottom E string.
| $6.6 7 |