The roots of polynomial $ p(x) $ are:
$$ \begin{aligned}x_1 &= -1.8393\\[1 em]x_2 &= 0.4196+0.6063i\\[1 em]x_3 &= 0.4196-0.6063i \end{aligned} $$Polynomial $ -x^3-x^2+x-1 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.