My commiserations - I remember the frustration, this is what I found
Align the item on the soldering pad, and the roller catch in a pair
of locking tweesers, so that you can comfortably place the roller
catch in the correct position at the right moment. The roller catch
is best gripped by the ears of the roller with fine-pointed locking
tweesers; gripping across the body of the catch can cause it to
distort when hot, and even fuse slightly if overheated, so true up
your tweesers and grip on that tiny ear!
Flux the spot where the catch is to go on the item, and the base of
the roller catch - I give the roller catch a quick blast of heat
before fluxing so that the flux adheres nicely on the base.
Place a pallion of solder on the item. Now, about the solder - extra
easy is a no-no, it runs all over the place and into the catch if you
are not very careful; and the catch will float and spin around when
re-melting. Easy solder is OK, but the best is medium solder - it
will flow slowly, and fill gaps nicely (eg if the catch needs to be
tilted, or soldered on a precarious edge). When re-melted, medium
solder remains sluggishly in place while you nudge the catch into its
Holding the tweezers with the catch locked in, do a trial
positioning on the item, then hold it away while you heat the item.
When the pallion begins to melt, place the catch on the melting
solder - it should bond almost instantly as the solder melts fully;
remove heat, unlock tweezers.
Check the alignment: if the position or angle needs adjustment, heat
the item (once the catch is soldered it will not overheat so much),
and nudge the catch into its final position with the solder pick.
Even if the catch is positioned correctly I do a quick remelt to let
the catch settle on its own while free of the tweezers, but keeping
the solder pick close by just in case. Good luck.