CSSをカスタムして使ったデモです。
<div class="container" data-rola-trigger data-rola-scrub-start="top top" data-rola-scrub-end="bottom bottom"> ...</div>
.container { position: relative; padding-block-start: 4px; &::before { content: ""; position: fixed; z-index: 1; inset-block-start: 0; inset-inline: 0; block-size: 4px; background-image: linear-gradient(90deg, rgb(131 58 180) 0%, rgb(253 29 29) 50%, rgb(252 176 69) 100%); scale: var(--rola-progress, 0) 1; transform-origin: left center; }}
new Rola("[data-rola-trigger]", { scrub: true});