So Archiveteam (a group of volunteers that archive dying websites) is very aware of RootsWeb's stuff going down in April. Fortunately, at least for the mailing lists, a WARC was made in 2021 by them (information on WARC files). That being said, you should still save all content you have in the Wayback Machine.
I do this basically every day, so I do have some tips.
1) If possible, make an account on Archive.org.
(This is what it looks like when not logged in).
I prefer to use it with my account, as I have several more features.
(The save outlinks, save error pages, and save screenshot options are the ones that I use the most. Also, a WACZ is a WARC file that is sent as a zip file.)
As you can see, this saves a lot of time. Also, saving a screenshot can be incredibly important, as sometimes, all of the embeds (so pictures, etc) do not load in the saved link.
For example, here is one that I just saved.
This part shows up, even if you aren't logged in.
(Link to snapshot) (Link to screenshot)
PLEASE note that you are only allowed a certain number of active Save Page Now sessions. Also, you can only save a URL once every 45 minutes. That includes if it is saved as an outlink. Not all outlinks are saved so please check!
2) The Wayback Machine browser extension is amazing. You should be able to find it on at least Chrome and Firefox (I use one for personal stuff and one for work, I have it installed on all my browsers). I believe it is on other browsers too.
This is particularly useful as it has many settings. You can choose to Save Page Now directly from the page you are on.
You also can choose an "automatic archive" function. I have mine set to automatically archive everything if it has not been saved in the last 7 days. (Though I can manually archive it if I so choose).
It is also really nice that they exclude URLs. They actually have a default list they save, you can add to it if you so choose.
Luckily, there is also a private mode, so you don't have to worry about EVERYTHING being saved.
I especially like this as it will automatically save anything I am viewing for genealogy purposes, including trees, Wikitree pages, and a ton of other things. Please note that archive.org can't really get through a lot of paywalls (so stuff like Ancestry is kind of a nightmare, but sometimes it works!).
Bonus: if a URL no longer works and they have it archived, it will give you the option to view an archived version of the site.
3) You can also email Save Page Now! It will save all of the links in the email -- unfortunately without outlinks. If you're in a rush, though, and just want to save the links you got in an email, you can forward the email to savepagenow(at)archive.org and it will save those links. Here's a blog post they had about it.
You will receive an email back from them about it, I do recommend either deleting those emails or sending them to a folder you make specifically for save page now emails. Sometimes if you get errors the system will email you a few separate times -- they process it a few times to make sure that they saved all of the links.
Here's an example of an email I have gotten from them recently:
Personally, I do two things with the Save Page Now email address.
One, I forward all of those Wikitree emails I get to it. This saves all (or almost all) of the profiles that are linked in there to the Wayback Machine, making them a trusted citation. I also forward all the blog posts I get from peoples genealogy blogs.
Two, I occasionally just copy entire webpages or make very long lists of links and email them to the SPN email. This is super useful, especially when it comes to my next point.
4) Sitemaps. You can either find the sitemap for a website or generate one yourself if the website is small. Usually it is called sitemap.xml, but sometimes it is called other things. I generated one for the rootsweb page I linked earlier. Here's a neat link about how to find a sitemap. (This is for people who own the websites, but you can do a few of the options on that list). A neat thing about sitemaps is that they basically have every single link for the website on them, which means that is VERY easy to 1) archive the sitemap itself in the wayback machine or 2) copy the links and send them to the SPN email, saving each link individually. (You have to do 2 if you generate your own sitemap for the site).
Luckily, it only looks for links, so you can put in something like this (or something even more busy) and it will figure it out:
I seriously -- like, seriously -- recommend making a sitemap for a smaller genealogy website. There are free sitemap generators -- most have a cut off of 500 pages.
I used sitemaps to save my father's Rootsweb pages a year or two ago, as well as his new genealogy website. It was very worth it, especially as a large number of Wikitree profiles mention his old Rootsweb site.
5) Other options. The Wayback Machine is not perfect. For some websites, they do not allow you to archive their content on there, or the paywall stays up after archiving. Personally, if I catch a website doing that, I usually try and archive with a different website. My preferred one is archive.today, which is currently being hosted at https://archive.ph/.