I am very sorry about the loss of you Watson. Honestly, a great way to go, quick, without issues, although I imagine it must have been a shock to you being the quick, unexpected loss. We recently had to put our doxie down - I feel for your heartbreak.
I can't help with the girl to girl thing as I have 2 boys. TBH, I'm scared of introducing a female; my husband does want one at some point though. I've always had boys except my first dog when I was young.
My only input is don't always expect love at first sight! You may want another, but Roxy may be super excited over the puppies or not interested at all. She might take a liking or take offense! It may seem like a cool thing for her when she visits and then she may be floored when that ball of energy enters your home. You know your family set up, you know Roxy, and you might feel a fit for your situation - go with your gut and all will work out.
We did not take Brodie with us when picking out Deacon; we took our youngest son. The breeder had 2 choices based on what she felt would work for us based on what was available. Hubby like one pup, son and I liked the other which was the one the breeder felt was best fit for us. PS. He is! Brodie was not a huge fan of him when younger. There was no animosity, but Brodie pretty much ignored him for months. Deacon would jump through hoops, literally jump, jump, jump trying to get Brodie's attention and Brodie would just look through him like he wasn't here. Once Deacon got a bit older and bigger, Brodie got more interested in him. They can each survive on their own, or on their own with one or both of us, but they play a ton together as well. They are not latched at the hip to each other but they are our Frick and Frack, two peas in a pod at times, not all the time. Brodie has never been a fan of yappy, jumpy dogs (even though he is a yappy, jumpy dog) and having Deacon around who is a bit less yappy but very much a pogo stick dog has made Brodie a bit more excepting of other yappy, jumpy dogs.