Jay, one of the main messages from reading the forum is that we all respond differently. You have to be aware that what happens to you won't be the "average".
However as others have said, without a prostate there isn't ejaculation. Semen mostly consists of liquid secreted by the prostate and without the prostate that doesn't happen. Nor is there the sperm from the testis or the fluid component from the spermatic vesicles, those have been disconnected (and in the case of the spermatic vesicles, usually removed).
Immediately after surgery you won't be experiencing erections - if nothing else you will have a catheter for a couple of weeks. There will almost certainly be bruising to the nerves supplying the penis, which run either side of the prostate, assuming the surgeon has been able to preserve them. If they can be spared there is a possibility that they will start working again, allowing erections, in the first few months. However it is more common for it to take six months to a year or more before anything like normality in a sex life. And if one or both nerves can't be preserved - usually because the cancer is too close to the nerves, though in some cases because issues in trying to preserve the nerves become apparent during the operation - it can be partial or not happen.
As others have described, there are people on this forum who have found ways of working round problems when erections don't return naturally. And you have to remember, if you look for experiences on the forum, that those who have the best recovery tend to get on with their life and are under-represented here.
If you are currently in the position of deciding what to go with, my best wishes because in some ways it is the hardest point in the process. The success rates in terms of cancer are all around the same, it is the side effects which are different and you don't know in advance which side effects you personally will experience. There isn't a "right" answer! In general terms younger men have a better likelihood of good recovery from surgery and older men are less likely to experience the delayed side effects from surgery during their lifetime but only you can decide which risks you are happiest with.