Toss the bell peppers, onion, tomatoes and asparagus with the olive oil, salt, and pepper on a large sheet pan. Roast for about 30 minutes, until golden brown, turning once with a spatula.
While the veggies are roasting, cook the orzo in boiling salted water for 7 to 9 minutes, until tender. Drain and transfer orzo to a large serving bowl.
When the veggies are done, add them to the pasta making sure to add all the liquid and seasoning, too.
For the dressing, in a small pitcher whisk together the lemon juice, olive oil, salt, and pepper. Pour about 1/2 of the dressing over the pasta and vegetables. Be sure you toss orzo with dressing while the orzo is still warm. This helps all the lemony dressing flavors infuse into the orzo.
Let pasta cool to room temperature.
Add the scallions, pignolis, feta, and basil.
Taste and season with extra salt, pepper and lemon juice if needed. You can also toss with a bit of the extra dressing if needed. If you don't use all the dressing it will keep in your fridge for one week.
Serve at room temperature.
This salad can also be made a day ahead and stored in the fridge. Bring to room temperature before serving.