A Buddhist monk or nun holds a vow to keep their hair shorter than the width of two fingers and not to wear jewelry, perfumes or other adornments. Since his three year retreat, Geshe Michael Roach has worn his hair very long as well wearing bangles and other pieces of jewelry.
Geshe Michael Roach claims that wearing long hair and jewelry is to help “trigger” his final transformation to Buddhahood (he claims by his actions to be an 8th level Bodhisattva). In other words, he wears the hair and jewelry of the Buddhist Deity that he wishes to become.
So too nowadays
To help to trigger
The final transformation into
The Diamond Sow herself,
I wear my hair
As the Angel Herself does,
And her bracelet
And other accoutrement
Together with my robes.
— Geshe Michael Roach, Letter to Lamas, 16 January, 2003
In the past, in India and Tibet, it was not unknown for lay meditators to take on this outward appearance, however there is no tradition for ordained monks and nuns to do so as it is against their vows.
In the early days, Geshe Michael Roach’s root lama, Khen Rinpoche Geshe Lobsang Tarchin, told Geshe Michael to keep his hair long and wear lay clothes when working in the west. This is, technically speaking, breaking a monks vow, however it is considered acceptable to have slightly longer hair so as to fit in with society and not disturb peoples minds.
Some years ago, Geshe Michael Roach undertook three year retreat with a small band of students. During such a retreat, it is instructed not to cut the hair or nails. This is done for various reasons, one of them being to save time preening which can be spent meditating, and also to break the attachment to preening itself.
Many Ngagpa (or lay) mediators grow their hair as such in retreat and do not cut it after the retreat is finished, however it is usual for a monk or nun to shave his head and remove any jewelry after retreat is over as this is one of their vows.