First off, welcome to the community and thanks for taking an interest in Roots! @seb2point0 did a good job explaining the difference between the tools and answering your questions. I just want to chip in my thoughts as well, to help clarify what Roots is and how you can benefit from the tools we build.
From the homepage:
Tools for modern WordPress development.
Roots helps you build better WordPress sites.
This promise is for developers and those who benefit from the work of those developers. Roots empowers developers, because developers empower others. As a non-developer, you can totally benefit from Roots, however, you must either be working alongside a developer who is using Roots, using a platform which uses Roots underneath, or be willing to learn some code so you can use the tools themselves. In the first two cases, as a non-developer you won’t need to think about Roots, because developers or platforms who use Roots empower you to just do what you do best — build websites with page builders, not focus on the underlying code of the website. If you do decide to learn the necessary skills to use the tools themselves, I’d say Roots is an excellent community to learn (I’m biased), however, the required learning for the skills you will need to do to use the tools will need to take place through resources and support which Roots and this community does not provide.
It is your own decision, however, if I were in your situation I would opt to work alongside a developer or a team who empowered me to do the best at what I already did. I’m biased, but I’d wager that the Roots stack is the greatest set of tools for them to do that.
On page builders and the Roots stack
The tools which Roots build — Sage, Bedrock, and Trellis — are not at all incompatible with page builders or designed to replace page builders. In your case, Elementor Pro Page Builder is a plugin which can be used with Sage — our starter theme — however, Sage is a solution for custom theme development — a task which requires coding knowledge. If you don’t want to learn the skills to do that or are not working with a developer who can do that for you, you’d be better off using a theme which supports your choice of page builder out of the box.
If you are using Trellis, then you will be using Bedrock as well, however, you don’t have to use Sage as the theme alongside those two. You can work on top of Trellis and Bedrock with a theme which is already suited/compatible with Elementor Pro Page Builder or whatever page builder you choose to use.
One thing to note is that, within Bedrock, plugins are treated as software dependencies instead of something which non-developer users can freely install. You will either need to install the plugin the Bedrock way or work alongside a developer who would handle this for you.
On Trellis and Bedrock vs. fully managed WordPress hosting
Trellis and Bedrock is an attractive option for those with development knowledge or working alongside people who have that knowledge, because they provide a very maintainable and secure WordPress install on a server which is specifically designed to host it for a very affordable price if hosted on a VPS (usually anywhere as low as $3.50-5.00 USD per month). That pricing is attractive, however, you ought to know that you are required to maintain and manage your own server and that cost will depending on your own capability to handle that task. There is no guaranteed support; the community here is an excellent aid, but we help out here out of the goodness of our hearts.
Roots is not just for developers
I don’t want you to feel like because you are not a developer that you cannot benefit from the tools or this community, because you totally can. If you want to use the Roots stack, but want to stick to what you already do best, then you’ll find that this is a great place to find others to work alongside with. Us developers can definitely benefit from non-developers who see the value in these tools. jobs is a great place to find others who are looking to collaborate.