Hello Dinnerlinner. I've been doing some searching to see what I could come up with for you. What I learned is that roving yarn is just a yarn that's not twisted like the regular yarns are however there are loads of chunky yarns available that can still do the job. At least I think so anyway.
The other thing is, there's a great website called Yarnsub. If you need to substitute a yarn you enter in the name of that particular yarn and it will bring up a great assortment of other yarns you can use instead. Here's the link: https://yarnsub.com/
That said it didn't help a whole lot in this situation because they came up with alternatives with the same content of acrylic and wool. Of course it makes sense. I still wanted to pass on the link to you because it works really well. If for instance you wanted to substitute Red Heart Comfort yarn you could enter that in and find out what yarns you could use instead.
Anyway I came up with a few suggestions you could try. These are all chunky weight yarns only they aren't roving but for what you want to make I think any of these will work out fine.
Zettl - Fontana Scarf Knitting Wool
I know it says wool but it's 100% Acrylic yarn and very close to the same consistency as the Bernat Roving.
James C. Brett (5-Bulky) I have some of this yarn and it's simple lovely.
Bernat Softee Baby Chunky Yarn 5 - Bulky and 100% Acrylic
Even though it says baby there's a wide range of colors that aren't just for babies
Red Heart Comfort Chunky Yarn 5 - Bulky 100% Acrylic
I hope this helps a bit. I'm so glad you're getting back into knitting. It's a wonderful hobby. Happy Knitting!