I am new to RoR as a scrum master and I am not sure whether RoR alone is okay for our web dev projects. The company I work for uses RoR already but I keep receiving proposals from web dev vendor teams on using other languages (Node.js, React.js, Laravel, Vue.js, Python). Is it fine to use RoR exclusively and dismiss the other languages for this company?
As a Scrum Master you should not be making this decision at all. Your job is to "remove impediments to the ability of the team to deliver the product goals and deliverables". And, I do not mean to offend, but your question shows a lack of understanding of the subject. You're new to Rails. And you've mixed up programming languages (Python) with frameworks (Node.js, React.js, Laravel, Vue.js) and back end considerations (Python, Laravel, Node.js) with front end ones (React.js and Vue.js).
Technological decisions such as which frameworks and languages to use are not to be made by the Scrum Master. If you have any role in these decisions, it would be to educate yourself on the topics (possibly by discussing them with your technical team members), and to facilitate discussion and making of a choice by the stakeholders.