Vanishing Density of Realizable Rolle Words

Let b_n count the nondegenerate orders of all derivative zeros satisfying Rolle interlacing, and let a_n count those realizable by ordinary degree-n real polynomials. We prove a_n <= (D_n+1)(2D_n+1)^n for D_n=n(n^2-1)/2. The classical enumeration of b_n then yields log(a_n/b_n) = -n^2 log(n)/2 + ((3/2)log(2)-1/4)n^2 + O(n log n), so the proportion tends to zero. The proof combines derivative-resultant collision loci with Milnor's affine component bound. This answers the auxiliary asymptotic question attributed to Arnold by Shapiro and Shapiro, Section 2, Problem 1. It does not classify individual words and does not close the broader frozen record AMR-021-0017. Prior enumeration, resultant methods, and two-level realization results are explicitly credited. Includes complete written proofs and portable exact checks. AI-assisted self-audited preprint; no independent peer review, formal verification or absolute-priority certification is claimed.