At least from the photo, it looks like deliberate decorative detailing.

I thought the same thing. They look to be perfectly alike and evenly spaced.

Got a picture of your roof installation? I'll bet the lines line up with the roof jack installations. Took a little more shingle to make it over the jacks?

Maybe they shingled from the top down and the lines are where they had to tuck the shingles. That would explain the consistency of the lines better than my roof jack theory.

You asked about what is causing the lines. Are the lines there all the time? Did they just recently appear? Were they there when you bought the house? Have you just had your roof replaced? Is it all sides of the roof that do that?

I see patterns on the roofs of my neighbors when we have a frost or snow where the heat rises up and melts the frozen precipitation between the joists and makes lines that run laterally up the roof. But, that is not all the time.

I have never seen a roof do that. They sure do look perfectly symmetrical! I am going to suggest that it is the work of aliens who are signaling a safe place to land their alien spaceships.

Who else could get as perfectly symmetrical as that?

Quite possibly the joints from the roof sheathing. Is the sheathing 7/16" OSB or 1/2" Plywood with no clips by chance?

Ask your roofer.

agree with Chessie. Either the previous owners, the builder or who ever installed the roof should have a much better answer.

it looks like most of us are just wildly guessing.

I am still going for the alien landing theory.

Look like you have an extra row of roofing material at those lines. Looks intentional to me.

I have seen these feature lines on a wood shingle roof. The typical way to achieve it is to lay down a line of cedar/ redwood bevel siding and shingle over. Gives a wide reveal and makes for an interesting roof.

ETA that this roof looks like 3 shingles were stacked with a narrow exposures to create the built up line.