Rub Roast Before or After Searing? I just put the roast beef in the oven and I don't know if I ruined it already.
So, what happened:

I lavishly applied a rub of salt, black pepper, dried rosemary, and fresh garlic to the meat prior to searing. Then I tried to sear it in the pan. The crust of herbs got darker and darker but the meat underneath was still quite raw, until finally the kitchen filled with thick smoke as the herbs started to blacken and got charred. And I feel kind of dumb that I didn't see that in advance.
I tried to make the best out of the situation, scraped the burnt herbs off, applied fresh herbs and put it in the oven at 90°C as planned.

Now the catch: The order of operations was dictated to me beforehand.
I painstakingly followed the rules set forth by my girlfriend - the rules for roast beef haven been handed down from one generation to the next in her family from ancient times, apparently Pharaoh Sethos I invented these rules and who am I to question them?
And the rules say: rub before searing.

Now I want to put the following question to the community:
Rub roast before or after searing? What would you do if you were not bound by any questionable ancient wisdom and a proto-sumeric curse?
I think there is a place for both. Without being aware of the particulars of this received wisdom/commandments from on high, it is a little hard to say. Seasoning of meat is often performed before searing (think steaks), but this is commonly only in the form of a thin layer of salt and pepper and maybe herbs too, not a thick complete covering. I have also seared roasts and then placed on a bed of herbs and garlic to roast - though not rubbed as such.

If you used seasoning as above and not a thick layer, then it would be reasonable to sear after rubbing. However, if you applied a thick layer so as to form a crust, these will have to heat up to searing temp before the meat could even approach a temperature at which the maillard reaction could occur. This would also be at or above the temperature at which the sugars in the herbs would also caramelize and start to burn, as happened in your case. In such a case I would not sear, unless in a very hot oven for maybe 5-10 min, before turning down to cooking temp.

It could also be that the family recipe only applies the rub to a portion of the meat, perhaps just the top/skin side, and only sears the bottom (or vice-versa I suppose).

Perhaps your girlfriend's family only use a thin layer of seasoning rub before searing.  It may be best to get an invite to her next family roast and ask to help in the kitchen while preparations are on-going. If you are looking long-term, incidentally this, and helping with the dishes, are a  way to get into the good books with her family too. Another option is to simply ask her how she does it!