Many Asyms come with a tack collar/strap that is meant to go around a headstay (or more likely a furled headsail). A
line from this collar to a block at the stem and run aft as per blt2ski is common as well, allowing adjustment of the tack height as you sail.
Generally you will lower the tack height to straighten the luff as your apparent wind angle decreases (ie you sail closer to the breeze)
If you choose to use an
anchor roller/stem fitting as the attachment point just ensure it's up to the task (remember that the major load will be in an upward direction as the sail tries to lift)