If this is the Amazon context you refer to,

The more Tchaikovsky's reputation grew as a composer, the more anxious he became to avoid public disclosure as a homosexual. He was a right old roarer apparently, specialising in boys in their early to mid teens.

it seems quite well-fitting with the slang definition of roarer

a male homosexual, especially one who is actually or supposedly flagrant.

I've not come across this word myself, so not sure how common this is in BrE

If this is the Amazon context you refer to,

The more Tchaikovsky's reputation grew as a composer, the more anxious he became to avoid public disclosure as a homosexual. He was a right old roarer apparently, specialising in boys in their early to mid teens.

it seems quite well-fitting with the slang definition of roarer

a male homosexual, especially one who is actually or supposedly flagrant.

I've not come across this word myself before, so not sure how common this is in BrE.

Without the full context, I thought roarer meant "someone who communicates vocally in a very loud voice"