The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -2.5468\\[1 em]x_2 &= 0.2734+0.5638i\\[1 em]x_3 &= 0.2734-0.5638i \end{aligned} $$Polynomial $ -x^3-2x^2+x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.